You didn't watch the 2nd video, which explains what happened here. Late sixties saw the rise of african-american gangs, and they gradually muscled out everyone else. Those black gangs are so violent and powerful now, we're nearly the only major American city that has no Bloods, Crips, or MS-13. All local, homegrown stuff.
The protaganist in the trailer is Black as well. Based on what we know about the game so far, they should have called it "Organized Crime", since it seems to be more about the demise of the Mafia in New Orleans at the hands of Lincoln. But, to answer your question, yes, the Mafia hired african-american muscle. Thats part of what led to the rise of black gangs. Why get peanuts when you can run the action?