why do i get game over when i reach high depravity?
It's literally stated at the start of the game, if you get too corrupted you'll give up and endlessly indulge in your base desire, and so will the whole city.
It's like Magical Girl Celesphonia, if you let the main character get too high of a corruption value (being 100/100 in MGC), you character loses her power and ultimately gives up.
You are the last vanguard against an invasion of depravity, and if you can't fight it no one can.
so you need to carefully balance your lust and the actual gameplay