The characteristic of the American mafia after Lucky Luciano is to have a structure and hierarchy to be highly organized compared to the other Irish, Jewish etc. gangs.

So heroin until the 60s the H or came from the Corsican mafia, which produced in asia or through Turkey arrived in Sicily that was full of laboratories for refining heroin.
In 1968 Frank Lucas directly procuring heroin in asia cutting out the middleman broke the monopoly of the American and Corsican Mafia.

Then in the late 70's and early 80s exploded consumption of cocaine. (just watch the movie Cocaine Cowboy to see how the money from the coke have changed the economy of Miami and Florida) and after the Pizza Connection Trial the American Mafia has lost its role in the distribution of drugs.

why he lost its role?

With the advance of the Colombian and Mexican drug cartels that are much more ruthless even the Sicilian Mafia, with increasing the punishment due to drug trafficking etc. simply the mafia families have collapsed.
Gene Gotti took 50 years and don't flip, Jack DiNorscio took thirty years and don't flip.
The new made men don't have the same force or intelligence of the old time mafiosi.

Also if until the 70s the mobsters had privileges in prison, now the idea of ​​being buried for 20,30 years in federal prison scares the strongest.
Including the risk of being attacked or killed by the first crazy with a knife or the protection money to the prison gangs (like gambino who pay the Aryan Brotherhood for protection)
And understand that it is better to earn in a month what they could earn in a week, but be free for enjoy the money.

The American Mafia, unlike the black or Hispanic cartels and gangs prefers to be invisible and earn as much as possible with few use of violence or murder (since you can be sentenced to life imprisonment as Alphonse Persico for 'murder Cutolo, even without a body, not to mention the DNA).

So families continue to make money with drugs but trying to avoid heavy sentences.

Why the mentality of a mobster compared to a member of a street gang is to make more money as possible and arrive at 70-80 years and retire to enjoy the money earned.
A member of a street gang knows that his end will be or die during a turf war or end up in prison, where he will be part of a prison gang (Black Guerilla Family, Aryan brotherhood or Eme for example) and will continue to do what he did outside.

Sorry if I have dwelt but tell me if I'm wrong