Say all you want, but in exposing himself he has proven that he is the DUMBEST old god yet. Cthun was already technically exposed a in the original war with the Qiraji in the effect that a large nearly unbeatable army was there so they sealed them away allowing him to gain power in the meantime. Cthun exposing himself was not even remotely foolish. Yogg gain control of what he though was the strongest force being the force that defeated them and it made sense to expose himself. Nzoth was barely even remotely freed when he exposed himself and had pretty much nothing going for him. Nzoth did not whisper anything to Voljin as he couldn't. His power is NOT even remotely that far reaching especially while jailed.
Every instance of "manipulation" you keep suggesting is 100% speculation and could easily be refuted. You have no evidence that the item itself was more than just a breadcrumb for the expansion much less that he could even use it to manipulate someone....while 100% jailed on top of that.
You've really given no evidence of actual scheming or manipulation short of getting Xal to get the player to work for them which was more her doing than his.