"Joker" is, in essence, a story about how the protagonist, Arthur Fleck, is gradually pushed step by step from his initial cowardice into becoming the Joker.
This kind of transformation is not easy to handle; aside from requiring a logical plot, the actor's performance must also convince the audience.
Especially for a character like Arthur, who hides a mad heart beneath a seemingly normal exterior, showing his madness step by step is a tremendous test of acting skills.
Chapter 540