Imagine the perspective of the cult for a second.

So, imagine you're one of the three chosen of the Absolute, you have an elder mind, and a whole bunch of power in your name. Everything is going well for you, you've got everything you need to deal with Baldur's Gate and all the factions that reside in the lands.
That is, until a Nautiloid crashes just near the druids grove.
Of which, a random ass person and a githyanki and a cleric of shar come out of.
That same random ass person then goes on to (over a relatively short time of lets say a week or two considering the ammount of long rests one takes over a playthrough) takes out the goblin encampment singlehandedly, saves that one druid y'all captured, converts Minthara over to their side, either goes through the mountain pass or the underdark and survives to get to moonrise, infiltrates into the system, finds (and likely kills) the necromancer you needed and also releases the source of immortality of Ketheric.
All in around a week or two.
And they are not even slowing down. Somehow they win every battle, kill every foe they need to, have such good skills that they have to be using some sort of artifact but to your knowlege isn't. And it's just a group of very specific people with funny tadpoles in their heads, the very ones you've been experimenting on.
Personally, I'd fake my death and GTFO as soon as possibe before they come after me next.