>>99487271Because his fall was a slow process of becoming more and more reckless and cruel in his methods when operating as Batman. He was getting older and more cynical, he's lost almost all faith in his mission because he had began to think he hadn't accomplished anything truly lasting in his years as Batman. He wasn't tracking down criminals and murdering them in their sleep, his focus was solely on finding a way to kill Superman for year and a half.
As far as we know Joker had been laying low all that time between MoS and BvS, so there was never even a moment where Batman would have had a chance to go full Tim Burton on his ass.
