We'll always have criminals. We'll always have organized crime. It's always been that way and it always will be that way. We can though create situation where crime flourishes, where organized crime grows. We did it with Alcohol Prohibition. That was a heyday for organized crime. Street gangs became very powerful organizations. A lot of people were getting rich and this attracted a lot of folks who weren't really professional criminals, people who probably wouldn't have engaged in criminal acts without all the opportunities and temptation Prohibition provided. When Prohibition ended, most of the people involved did not just move on to some other kind of crime. The mobsters did. The professional criminals did. But there were millions involved in one way or another who did not go on to other forms of crime. My grand dad cooked up a little hooch in the woods with his brother to sell to supplement his income from his carpentry business, and after Prohibition they became contractors building homes and eventually whole subdivisions. A guy like Joe Kennedy had money to finance alcohol smuggling operations that made him a lot more money and after Prohibition he focused on legitimate businesses and politics. We had bootleggers who became stock car drivers. Prohibition created a lot of opportunities for people to make money, it created a lot of temptation, and millions of people were involved to varying degrees with the production or smuggling of alcoholic beverages, transporting them, selling them and so on. Most of them didn't move on to other criminal enterprises after Prohibition and the same would be true if we did something like legalize marijuana. The billion and billions of dollars being made in the illegal drugs industry does fuel criminal behavior.
When basically moral people get desperate, they sometimes do “what is necessary” to survive. That’s human nature. The problem arises when societal morality erodes to the point where corruption takes root as a way of life and as an acceptable norm. That is an entirely different sort of problem and history has few examples of societies extracting themselves from such a trap peacefully. Mexico has long crossed this line and the real danger to the USA is that this culture of corruption takes root here.