One of several key factors (sup RICO) in the failure of the Mafia was the weaker families, primarily in the Midwest of pizza fame as the spread of delivery enabled the right pizza boxes to be filled with drugs, so if you can find an alternative illegal non-drug business for weak crime groups—or make weed acceptable—the Mafia can almost stay together.
The East Coast was big and powerful without touching drugs. Over in Vegas the casinos powered things. In Hollywood MCA was the go-to, Paramount joins in as the 1970s go by. It’s the dumb ass weak and flailing Mafia families that get involved in the drug business.
And then, naturally, the bandsaw of War On Drugs just spread and spread to crush the Mafia.