I agree with you. I think drug trafficking is the main source of income for criminal organizations.
There are different levels of involvement in the narcotics trade. Criminal organizations such as the Mafia or the 'Ndrangheta are involved at the level of importation; motorcycle gangs are involved at the level of distribution; and street gangs are involved at the level of drug retail or selling on the street. This is the way that criminal organizations organized themselves in consolidating this major source of income.
But I believe another important source of income is money laundering. We underestimated the importance of money laundering in the lives of criminal organizations. It's practically impossible to run a criminal organization if you don't have an avenue to launder money. You can't stash money in cash. And I believe construction is a great way to reach legitimacy. When we deal with money laundering, and when we deal with a way to find a cover for your criminal activities, you are looking at corruption and infiltration. That's the way criminals and sometimes politicians and businessmen meet together for different reasons.