I have my own opinions on how to stop drug cartel and the black market which surrounds the drug industry, but as to the "what stopped the mob gangs" question....
Ask the FBI you will likely find their answer to be "uhh....nothing". They still maintain a very busy organized crime unit. Point is the mob is alive and well, along with many other forms of organized crime (i.e. Outlaw motorcycle gangs, Russian maffia, MS13 style street gangs etc)
There is no doubt that the mob is alive and well. Billions of dollars in illegal drugs don't make it into the US every year behind the organization of a bunch of stoned high school drop outs. Ever wonder how such a high volume of drugs gets moved with so little violence? It's amazing ain't it? When was the last time there was a drug related shoot out between law enforcement and drug runners in the US? It is a very rare thing.
My uncle was an FBI narcotics special agent of some note and considerable reputation in Las Vegas in the 70's and 80's. He even made the cover of Newsweek at one point, and was the special technical advisor on the movie "Casino". That was his case, and virtually everyone in the move was dead or in protection. He was the perfect person to tell the story, and even got himself on screen for about 20 seconds (he arrests Joe Pesci's wife and even says his name).
To tie this into the gun thread, even when he arrested all of these guys he never had to use his gun. Not once. He never felt threatened. He used to talk to them all the time. Vegas was a small town then, and they would run into each other all the time. The mob knew they were crooks, and the FBI was out to get them. It was cat and mouse. Business. The mobsters only killed people who ratted or refused to pay debts. It's still that way, here anyway. In Mexico, they will kill you for jay-walking.
uch_125: