In my opinion things for the Mafia began to crack right after the death of Carlo Gambino.
I agree, I think the "real" decline started in the late 70s. Also, after the French Connection was busted, the mob became even more involved in the distribution of narcotics, which brought more attention of law enforcement. The same happened with the mob's activities in Las Vegas in the late 1970s. I think the downfall of the Cleveland syndicate was a symbolic starting point for the decline of the American Mafia.
"It was between the brothers Kay -- I had nothing to do with it."
