Hitler hadn’t started stuffing people in ovens yet. And the Great Dictator wasn’t funny; it was actually horribly put together because about the time they were wrapping up production, Stalin signed the Non-Aggression Pact with Hitler so Chaplin was ordered by Moscow to add the ending scene where he admonished the audience “this is not our fight.”
You are right and there was nothing comical about Stalin and his atricities. But the worst thing dictators hate is when people make fun of them. I hear, Hitler was very pissed at the Dictator, its pluses or minuses aside.
To my prevoious point, people in Russia were sent to Gulag for jokes or even typos associated with Stalin or his name (like Stalingad instead of Stalingrad). The editor-in-chief of that paper was arrested and sent to Gulag for that typo.