So, my character, Logan, is looking for answers. He stuck out in the great galactic void, far away form his home in the Milky Way. He wants to know more about the Universe, all of it, but it’s impossible. Even living in the 26th century, when the lifespan of humans is around 175, or even longer if you try our mind loading, it’s still a fools race. He can’t search every galaxy in the universe, even if he lived 15 to the power of 10 centuries. But, he has had the chance of billion lifetimes. He has found a divine being. It doesn’t look that holy, but it promises that, for a Microsecond, Logan will have all power and control over the universe, total divinity. He will be Omnipresent, on every single plane of reality, Omniscient, knowing everything their is to know, and Omnipotent, but only for a microsecond. He agrees and the deal happens. Logan, for a microsecond, is the god of the universe, but after, he has an epic, mind numbing seizure. My question is, since I can’t make an answer myself, why would a person so excited about knowing all the secrets of the universe have a seizure and go insane after?
A little bit of omnipotence goes a long way, just like how one fifth of infinity is still infinity there's no quantifiable amount of omnipotence, you either have it or you don't. So really what we've got to consider isn't why Logan had a seizure after his eternity of omnipotence but rather why did he give up his omnipotence in the first place?
Conveniently omniscience gives us an answer to this, imagine drawing a picture on a white sheet of paper with a black pen, while the sheet is blank there's a huge but not quite infinite number of pictures you can draw on it. If you drew all of those pictures at once the result would be a black sheet of paper, a drawing of everything that looks like nothing. My point is a single mind can't know everything at once, not because there isn't enough space (although that may be a limiting factor) but because information can be cancelled out by more information and when you know everything, everything you know is cancelled out.
Humans perceive a singular current moment, remember a series of past events and can only speculate about the future, an omniscient god perceives all pasts, presents and futures simultaneously. A mind can't function with that, you can't see what is because you're blinded by everything that could be, you see a ball falling towards the floor and you don't know if this is the reality where it bounces or where it shatters because until it happens both realities are exactly alike, and that's just two of an infinite number of realities.
You can't just limit your perspective to one reality because by the definition of being "all knowing" you not only know everything you know but also everything you don't know, which can never be anything because you will automatically know it, or again one fifth of infinity is still infinity.
So omniscience is useless, by knowing everything you're incapable of knowing anything specific. Likewise omnipotence is useless because if you don't know anything (not even who you are or the state of your own mind) how can you make decisions?
Logan's "seizure" started when he was omniscient/omnipotent and he hasn't stopped being omniscient/omnipotent since, indeed he never will. Meanwhile his effectively brain-dead body is doing what every animal does when you cut off its head, his nervous system (minus all executive functions) is going haywire, were he a chicken he'd be up and running about.
How can you not go crazy?
Now imagine the human mind as a thimble. Now cram the entire Pacific ocean into the thimble.
For a microsecond you have the entire ocean in there but it's going to immediately explode back out.
Now what do you think happened with the water that was already in the thimble?
These memories are the ones he uses to walk, talk, his personality, his past, his skills.
The human mind can only contain so much. The flood of knowledge would wash everything he needs to function right out.
The end result would be a vegetable.