Don't forget, Kimbo was also a college football player.
What's the big deal about the 4 guys being former NFL players? I went to college with some guys who made the NFL just on the practice squad. You can be sure you would NOT want to mess with those guys. NFL players, even on the bottom end, are "finely tuned athletic machines". No doubt, they could make the transition if properly trained. They may have been wrestlers or boxers in high school too.