Fan Theory Says Arthur Fleck Joker Is Not The Joker Batman Actually Fights

From the trailers that have been released so far, Joaquin Phoenix's Joker seems to be less violent and more of a catalyst behind social change.

A very young Bruce Wayne can also be seen in the trailer (around 1:47). This means by the time Bruce Wayne would become Batman and fight Joker at least 10 years would pass (probably more). It is well known that Joker in the comics is around the same age as Batman, which made people scratch their heads.

If Arthur Fleck is the same age as the actor that plays him (44), there would be no way that he could keep up with a much younger Batman, being around 60 years old. This made many fans wonder if this movie is connected to the current timeline or if it is a prequel. One fan on reddit came up with an incredible theory

The theory asks if the social movement that The Joker we see in this movie sparked is the inspiration that drives a much younger man that believes in chaos, violence, and anarchy.

The theory goes on to predict that this Joker will also take the same imagery and ideology from Arthur Flecks movement to shape his own goals.