Emperor is super powerful and is crushing the elves who were controlling the human race from behind the scene!
Nope! Emperor's forces are super-weak and have to flee from the Elves we just pissed off!
Emperor: Let's split my weak forces, so that I can get rid of the riff raff!
Emperor: BTW in my past life, although I was supposed to be super-strong, I was actually a figure head who wanted to rule over absolutely everything (even though I'm weak, and have zero for empire-management skills) along with my girlfriend.
Emperor: Oh no, lost the reincarnation of my girlfriend whom I was mind controlling to do what I want!
Emperor: Oh a door to a world in which everything is awesome! Great! I'm down for that!
Emperor (two years later): Well, maybe this was a little sus. And besides, my girlfriend isn't here.
Emperor: Whew! My few remaining loyal retainers are willing to sacrifice themselves so that I can escape! Great! Off I go! Back to the world in which I got rid of the riff-raff, and my few loyal retainers just sacrificed themselves for me! BTW, It's been two years since I left... Well, I'm sure everything is fine.
Emperor: Oh, the sus people who tricked me into this world are now telling me it was all just a test! And now I'll get a reward from some Emperor (not me) whom I've never heard of? Sounds Great!