Bruce Wayne, who hasn’t even hit double digits in age yet, still has a lot of pain to process from the event, and a lot to go through on his personal journey.
That’s not Joker, though, and the murder of Thomas and Martha Wayne at the end of the film affirms that.
But meanwhile Arthur Fleck has already finished his own particular search for self-understanding and has become who he has meant to be.
He potentially has years and years of death and mayhem ahead of him before a vigilante dressed as a bat starts to try and stop him.