Undoing Mundus is definitely not mentioned in-game.
It does make Ancano make more (or any?) sense, though.
Think: barely veiled contempt and obviously shady behaviour is more justified when he just needs to get his hands on the reset button for like a few hours. "Screw traditional espionage, these idiots don't understand what the Eye is all about. Who cares if they suspect me? We'll all be vapour in a few days."
It also just feels right. Elves tried ruling over men before. Power shifted and they lost out. Why share the prison cell when you can just kill the other group of inmates? And better yet, why not bust out of jail when the opportunity is staring you in the face? If Mundus is a prison to the Altmer, and they want to be like Auriel and get away, why not just tear the walls down? That's not even punk rock, it's just good government.