The Endbringers acted as Eidelon's "worthy oppenent" until he died and after he died, they defaulted to their original directive from Eden of preserving the cycle so they seem to be loyal to their directive.
This isn't true.
First, Eidolon's High Priest is directly called the Endbringer's creator by the Simurgh's PoV. Though Eden's vision features Endbringer-like constructs, they are different in both form and function (being there to separate the continents and breed antagonism by enforcing that separation). We can extrapolate that the building blocks were already there and High Priest simply put them together, but the Endbringers, as they exist during Worm, explicitly were not made by Eden.
Second, the preservation of the cycle is explicitly the Simurgh's self-appointed task, not a group thing. We don't know what the others want because they don't live long enough for that to matter in the end.
Third, until Scion informed him, Eidolon was unaware of any connection. Despite the fact he was going at 100% and essentially flipping through brokenly OP powers like it's one of those "flip to animate" books, meaning there had to be some OP thinker powers among those, too. Meaning that even as he was grasping his powers to nearly their deepest extent, he was unable to make the connection until it was pointed out to him.
The following is somewhat speculative, but the description of Glaistig Uaine about why she calls him High Priest, how his power doesn't order or limit (as Queen would) but instead guides through less direct, almost religious methods imply that there simply is no connection with the Endbringers once they're made. They follow what High Priest says like zealots follow religious figures, and you can just look at history to see what sort of disasters that brings to, or in the context of Worm, the destructive fervor the Endbringers had (destroying society and ravaging the planet in a handful of decades as opposed to the centuries the cycle is expected to last) even when that's really not something Eidolon wanted.
This might even be a basic design feature that Eden was going to make use of with her "not-Endbringers", by making creating iron-clad plausible deniability from even the most advanced tinker-tech detection systems, only being able tobe sussed out by someone taking a real big picture look.
In short, and tying this back to this story, getting Endbringers involved to somehow police ascension is kind of foolish, in that at some point they will become the problem, whether by dogma entrenching itself, self-determination and deciding to do their own thing, and so on.
It'd be equivalent to just asking some of the already powerful people of this world to do it, it'll work, for a time, but there's really no guarantee that actually fixes anything permanently.
IMO, more likely is something like what's happening right now with Penance: information and weapons stashed away for just-in-case scenarios.
