He's a method actor. Maybe he stays in character for a while after the movie is done.
"I don't drop character till I done a DVD commentary."
A very good observation. The award went to Joker...so Joker accepted it, weaving in and out of Joaquins twisted reality. Note that he called himself a scoundrel, hard to work with...and if it wasnt for acting, hed admittedly be nowhere in life. There might be some guilt showing over the fame and success he has fortunately earned.