The irony is that he thought a communist dictator would be better.
The Great Dictator was a terrible movie. When first conceived, it was intended to be an anti-Nazi movie. However, during production, Chaplin’s master signed the Non-Aggression Pact with Hitler, so the tone had to change, and the message got a bit...”confused.” At the end of the movie, Chaplin informs his viewers “This is not our fight” in a plea to not come to the aid of Britain. It appears the movie was released about 9 months too soon. Otherwise, it would once again have been virulently anti-Nazi.