The Group of Four's rise to power
They aren't concerned with the loss of their power initially. In fact, nothing could be further from their minds. They are utterly confident in their power to control the situation and allow Clyntahn to convince them to whack someone who is simply irritating. He obsesses not over the threat to his power but over the affront to his power which Charis represents. He's been worrying about the "independence of thought" of those distant archbishoprics primarily because they aren't kowtowing to him sufficiently, and he is also at least a little better aware than the others of the Reformist tendencies within the Church. Even he vastly underrates them, however. Indeed, the disasters into which the Go4 stumble are the result of his persistently over-estimating his power and his ability to "make things be the way he wants them to be." By the time the reality begins to dawn on him (and the rest of the Go4) they've already created their own monster (sort of Jason without the hockey mask) in the person of the Empire of Charis and they have unleashed the true threat to their power --- the Reformist tendencies of the people of Charis in general. At this point they are obsessed with threats to their power, and quite properly so.
I was answering the original post in a hurry because I had to take my son to his baseball practice --- one reason we had some of the typos we had in it.
I was also responding specifically to the attitudes and beliefs of the Gof4, not the Church as a whole, and I think a more thorough discussion of where the Gof4 came from and what motivated its individual members might be in order. This is especially true of the Grand Inquisitor, since Clyntahn has been the driving force behind so many of the Gof4's policies and actions.
Clyntahn had several driving motivations beyond simple pique at Charis or “fear” of Siddarmark, and he's a firm believer in killing as many wyverns as possible with a single stone. Let's look at some of the aspects of what the Gof4 is, how it came into existence, and exactly what Clyntahn's role in all this is.
The Gof4 has zero official, legal standing as the determiners of Church policy. Its members didn't exactly set out as a group to “seize control” of the Church; instead, these are the four men who wound up accumulating a terrific amount of personal power because each had risen to the head of one of the four primary bureaucracies of the Church. In effect, they were the Secretary of State, the Secretary of the Treasury, the Secretary of Defense, and the Attorney General and Supreme Court (in one package) under a President with absolute power and a lobotomy. That's actually a little unfair to the current Grand Vicar, but not a lot, and the fault in that instance belongs to Trynair, yet it was actually a defensive maneuver on his part.
What may not yet be fully evident in the books to date (but should be clear at least by the end of Foundation) is that the votes were cooked when Clyntahn was selected as Grand Inquisitor, and the guy who handled the tactical details of the ballot box stuffing was our good friend Rayno which has something to do with his present position. The true winner of the election (though no one actually knows this in the books) was Samyl Wylsyn, which is one reason for Clyntahn's pathological hatred for the entire family. This was something like the equivalent of Heinrich Himmler taking over the SS, except that when Himmler first took over the SS, it was a very small cadre within the SA whereas the Inquisition was the SS at the height of its power when Clyntahn was “elected.”
The Inquisition was already corrupt (one reason Wylsyn was running for the Grand Inquisitorship; he wanted to reform the abuses he saw), which had a lot to do with how the election could be manipulated in Clyntahn's favor, but Clyntahn took it to a whole new level. He took a corrupt institution (corrupt in the sense of individual abuse of power and a steadily increasing tendency towards arbitrary decision making, bribe-taking, and the use of the iron fist to suppress dissent and/or resistance to that power abuse) and gave it dynamic new leadership which took it in the direction of his own particular brand of intolerant zealotry. I'm not saying he completely created the “new” Inquisition in his own image or that the “old” Inquisition was somehow benign or “kinder and gentler.” What I'm saying is that the Inquisition (like the Church hierarchy as a whole) had been gradually slipping into a more decadent, power-and-wealth-loving, corrupt stew of political infighting and self-seeking cliques for a couple of hundred years and, in Clyntahn, the process met one of its poles. He was the consummate insider and manipulator of the decaying system, perfectly suited to seizing control of the most powerful and ubiquitous single arm of the Church, and reshaping it in accordance with his own vision. What made him especially dangerous was that he genuinely saw no divergence at all between his own narrow and intolerant views and the will of God. Worse, the cynical and pragmatic side of him recognized the power of terror as a means of discouraging or crushing opposition. Long before he moved against the Wylsyns' Circle, he'd already decisively crippled their power base within the Vicarate (the only power base that really mattered) by essentially terrifying all of the “fellow travelers” into getting out of the Inquisition's line of fire.
Trynair didn't see Clytahn coming. He expected Wylsyn to win the election, and when he realized what Clyntahn was up to, he cast about for a counterbalance in order to preserve his own powerbase. Fortunately for him, the Grand Vicar died before Clyntahn had fully consolidated his own power. Trynair's alliances within the Vicarate were enough for him to secure the election of his candidate, the current incumbent. That consolidated his own powerbase in the political side of the Church's leadership and policymaking, which --- on the surface --- actually gave him more power, more ability to shape the Church's agenda (at least in the traditional fashion), than Clynthan possessed. At the same time, however, he was aware that his power was more amorphous and indirect than Clyntahn's and that Clyntahn was still in the process of consolidating and strengthening his powerbase. At that point, Trynair made an alliance with Maigwair in order to bring in the Temple Guard as a balance for the Inquisition's coercive power. It wasn't that anyone expected there to be a direct confrontation between the Inquisition and the Guard; it was simply a matter of assembling offsetting powerbases with an eye towards distributing control of the Church and Church policy in accord with the de facto division of power.
In effect, Trynair brokered the Gof4 (only he originally envisioned it as a Group of Three), reaching an accommodation with Clynthan and Maigwair. Initially, Trynair anticipated that Maigwair would be his ally against Clyntahn; in the event, Maigwair proved a weaker reed than Trynair had hoped and Clyntahn's influence continued to expand.
The offset for that in Trynair's eyes was Duchairn, who (because of his control of the Church's finance) had a huge de facto powerbase of his own. Both Clyntahn and Trynair recognized that they would require Duchairn's participation if their alliance was going to effectively control Church policy, but Duchairn had acquired his powerbase by being the consummate bureaucrat. Unlike Trynair or Clyntahn, he was a nuts-and-bolts kind of guy, a technocrat. He played the game of personal power, of course, and built his own empire in the Treasury, but he wasn't remotely in Clyntahn's league for megalomania or in Trynair's for Machiavellianism. In a way, Duchairn and Maigwair were both technicians *although Duchairn, frankly, was a far more brilliant and capable technocrat), while Trynair and Clyntahn were both political operators, which left the Chancellor and the Grand Inquisitor as the poles of power within the Gof4.
Clyntahn, in his competition with Wylsyn, had identified the urge for Reformism (which was still very much below the surface) with his opponent in the race for the Inquisitorship. He hadn't really identified all the components of the movement, nor did he realize how wide and deeply it had truly spread, but he was aware of its existence. Where Trynair was focused on Siddarmark as a potential (and fairly distant, long-term) secular threat to the Temple Lands (which, bear in mind, were officially secular states themselves), Clyntahn was concerned by the Republic's potential to support Reformism. It wasn't that there were openly “Reformist” congregations springing up everywhere or any organized movement in that direction, but the Republic's social and political organization (in his view) lent themselves to the possibility of such movements, and he actually saw signs of drift in that direction in places like Glacierheart. His inability to get his hands around the Republic's throat by threatening/coopting the aristocracy as the Inquisition did in most of the mainland realms made him automatically suspicious of it, just as the geographic distance between Zion and places like Charis (and the failure to cross-transfer so many of the local clergy, as was done in the continental dioceses) made him hugely suspicious of Reformist sympathies in those distant realms. Charis' wealth and hugely disproportionate and ubiquitous influence (because of its merchant marine and the power of its navy) made it even more visible on his radar screen than the Republic and only reinforced his suspicion of and hostility towards Charis. (Rayno was Clyntahn's man on the disputed Hanth succession, and the decision that panel handed down was really directed by Clyntahn as a move against Harahld because of that suspicion and hostility).
Clyntahn is constitutionally incapable of recognizing what is driving the Reformist movement completely irrespective of anything having to do with Saint Zhernau's journal. In his eyes, anyone who disagrees with him, who questions any aspect of his interpretation of the Holy Writ, or who dares to object to his harsh and arbitrary policies, is an enemy of God Himself. There is no distinction in his mind between himself and God; therefore, anyone who disputes his judgment (or might dispute his judgment) is a vile, willing servant of Shan-wei and deserves whatever happens to him. As Merlin himself observes, however, Clyntahn's instincts did not play him false in Charis' case: Harahld and Staynair were systematically working to undermine the Church of God Awaiting, to discredit the Archangels, and to embrace all the “heresies” of the historical Shan-wei. Clyntahn may have become suspicious for all the wrong reasons in Charis' case, but his suspicions were fully justified.
From the perspective of Trynair and (especially) Duchairn, Clyntahn's “Final Solution to the Charisian Problem” came out of left field and the decision was almost casually reached; from Clyntahn's perspective, it was anything but casual. There was a reason he assigned his own agent to Archbishop Erayk's staff, just as there was a reason for the way in which he presented that agent's findings to the other three members of the Gof4. He wanted to do exactly what he accomplished: to panic them into accepting his deliberate destruction of Charis. And he intended that destruction to be just as spectacular and complete as the Charisians think he did, both to punish them for daring to rebel against him (oh, and against God, too, of course) and to serve as a grim warning and horrible example to anyone else (like Siddarmark) who might be considering a similarly Reformist approach.
One point that needs to be understood, however, is that he did not react out of fear or out of any doubt of his own power or the coercive authority of the Inquisition and Mother Church. He was absolutely confident of his ability to destroy Charis, or he would never have acted in the first place, and the other members of the Gof4 were equally confident of their ability to destroy the kingdom and all its works. He managed to frighten them with the potential of what might happen if they didn't act, and he rushed them into agreeing with his proposed plan of action (largely because he was the only one of them who brought a plan of action to the meeting, since he was the only one who knew how he intended to shape and push the discussion), but not a single one of them doubted for a moment that they would succeed in their efforts. And none of them really considered the implications for the people of Charis, either. It was a theoretical discussion and decision for them in many respects because they had become so divorced from the day-to-day realities of the Church at the level of local kingdoms and congregations as a result of their high office. That divorce is, in fact, the thing for which Duchairn is unable to forgive himself now that he has experienced a genuine regeneration of his personal faith.
As a consequence of their failure to destroy Charis as planned, the Church of God Awaiting and the Gof4 now face a battle for their very existence. By eliminating the Reformist Circle in Zion --- and using the hideous example of what happens to anyone who questions Clyntahn to completely cow the surviving vicars --- the Gof4 has consolidated its control over the Church. There is no trace of any sort of organized resistance to their policies in the rest of the Vicarate and no new vicars have been named to replace those who were executed for “heresy.” No “new blood” which might dispute the Gof4's policies (or grow the courage to resist them) is being permitted into the Vicarate, and every present vicar knows that he will survive only so long as Clyntahn is convinced that he is not a threat. The Gof4's control in Zion is absolute at this point, and the other three members are finding it increasingly difficult to restrain Clyntahn, whose control of the Inquisition in time of jihad has made him unquestionably first among equals. Yet even as that happens, all three of the others are aware (though they aren't all necessarily to admit it to themselves) that it is Clyntahn and his policies which have created the very real and very deadly threat to their existence and the Church embodied not simply in the Empire of Charis but in increasing Reformist sentiment in other realms.
Where the Gof4's internal dynamic will go is not (of course) something I'm going to tell you at this point, but that's where it came from in the beginning and the reason for the actions it's already taken.