From today's perspective, boxing is well-engineered white demoralization propaganda.
Even biologically blacks benefit massively from the Queensberry Rules. That is Due to smaller lung capacity than all ethnicities in this world, which is great for anaerobic sports and whenever intervals are present, West Africans literally get out of breath sooner but need shorter breaks than East Africans or Europeans to fill their lungs and get up again.
African Americans usually have fast-twitch muscle fibers of type llb (8% less slow-twitch and 7% more fast-twitch muscle fibers). They produce ATP (adenosine triphosphate, look it up) at a slow rate by anaerobic metabolism and break it down very quickly. This results in short, fast bursts of power and rapid fatigue.
Means the short breaks you have in boxing actually do more for black people.
All that on top of things like having longer limbs, being more aggressive due to higher blood pressure and being more salt-sensitive.
Back then, because there weren't any rules, grappling was allowed. Grappling is the bane of a black in an actual fight. Blacks have very long limbs like apes, but a very slim waist. Their joints and ligaments aren't as strong as whites, but they are faster.
Whites have a very thick pelvic bone and proportioned skeleton, giving us a lower center of gravity for more raw strength. If you watch MMA or simply fights on the street, blacks HATE going to the ground or fighting up close. Most of the time they break up the fight if the black gets slammed.
In boxing, you'll notice throughout history that white fighters and some Mexcans always came straight foward with a crouching style, generating power with their slips, bobs, and weaves. Whereas blacks naturally back up, step to the side, and rely on hit and run tactics. It's rare for a black to stand in front of you in the boxing ring if you take it to him. There are obvious outliers in history like Tyson, Foreman, Shavers, Frazier etc. Even Ray Robinson and Joe Louis would trade.
But for the most part, the negro is incapable of close quarters combat. The negro always benefited for Queensberry rules, not having to fear from aggressive fighters. MMA showed us what happens to fighters who run when grabbing is allowed.
Fun Fact: most white bare knuckle boxers in the past were, in fact, very good wrestlers. Boxing and wrestling used to be cummulative with each other unlike today.
Another contributing factor of so many black boxsers is that gyms are always located near either black or Hispanic neighborhoods.