I mean, there are gangsters that play poker, and there are private games run by gangsters (I imagine), but the idea that the poker world is highly entangled with the underworld is pretty outmoded at this point. High level pros like Jungleman aren't going to risk their rep/access to other good games by breaking someones legs, even over a few million. He and his backers have the risk of losers defaulting baked into their EV calculus already when he plays those games.