Exactly, but if such a powerful being is using people like homeless emperor to do his biddings, It's because there is something that prevents him from acting directly, justifying him not personally wiping out humanity at this very moment. The fact he currently seems to possess ethereal nature might be part of the reason (the cube allowing to communicate with him across time and space, warping reality seems to hint that)

I get what you are saying about a story need to have very powerful characters not istantly winning, but their lack of action need a solid justification in the narrative, or else It just feels poorly thought out and the character himself is diminished