Ending Explained. The truth about the final scene!

Rating: 9/10 (9 October 2019)

This movie is one of the greatest movies ever made. Everything about the movie is fantastic. The acting, the plot, the twists, the music, you name it... But the most important thing, the ending, is something Spectacular!
In the final scene when Arthur is speaking with his psychiatrist he is in a mental asylum and his hair and beard are GREY, a sign of this being about 15-30 years later. When speaking with his psychiatrist, Arthur suddenly starts to laugh, but only this time, his laugh is very different from the laugh throughout the movie. This laugh seems a lot more "genuine". Arthur is having a flashback to the time when he was free. Then the psychiatrist asks him, what is so funny? Arthur then gets a new flashback, this time, of Bruce Wayne standing beside his dead parents during the riot caused by the joker. Then Arthur says "You wouln't get the joke". Since Arthur now has grey hair, this is some years later. During these, lets say, 20 years, Bruce Wayne has become Batman and got his revenge on the joker, who was the reason for his parents' death. Arthur finds this funny because of the irony. Arthur starting a riot, leading to the death of Bruce's parents, Bruce coming back, 20 years later, and locking Arthur inside the asylum. Arthur doesn't only find this funny, he also gets very angry and upset, which is why he kills his psychiatrist in the end. He is angry that his actions fired back at him and caused him to be locked up in a mental asylum for the rest of his life.
The joke all along, and the reason for Arthur calling his life "a comedy", is that HE CREATED the BATMAN.
Thank you.