On the contrary, science proves whites have the highest testosterone on average, which is why they're more likely to kill than the rest.
Source on this?
Bu-bu-bu-but he has supreme athleticism
In all seriousness somewhere around three years is more than enough time to become a solid MMA fighter. The fact that Brock Lesnar became champion in such a short amount of time (yes I'm aware of his Division I wrestling credentials from 10 years prior) and Jon Jones - a good but not transcendent athlete by league sport standards - looks like an athletic God compared to his opposition and did in fact win the title after 3 years is all the proof you need. The UFC roster boasts people like Roy Nelson in their top 10 divisional rankings and mediocre football washouts like Brendan Schuab and Matt Mitrione have become perennial contenders after training MMA for 3-4 years.
You seriously doubt knowing all that that a seriously gifted, once in a lifetime athlete like James with full time training couldn't take a mid-level, aging fighter half his size? One year might be a stretch but two years in and he'd beat down almost everyone in the sport.
The gap in talent/athleticism between the NBA/NFL elite and fringe sport guys in MMA is enormous. If MMA fighters were more talented they'd go to boxing and make millions instead of thousands in the UFC and Bellator.