The mafia in movies and TV shows being stereotypically Italian was the jews way of deflecting on to the Italians what was actually a jewish power structure. It was easier to put an Italian face on organized crime.

Best example of this is when they do movies on the mob, I'll use Casino and the Untouchables. Both of which involve jewish organized crime and jewish specific characters like Meyer Lansky in the Untouchables and Sam "Ace" Rothstein (movie name) Frank "Lefty" Rosenthal both played by Italian actor Robert DeNiro