I recall Mike Tyson saying that a few years back. I believe it is. And I believe we're all a little crazy for enjoying it!
I find I immediately get along with most guys even if we disagree. So we may all be on a spectrum of crazy of sorts that we can relate too.
No, it's not but there is something intrinsically mental about someone who willing wants to be punched in the face.
Complicated. Non-lethal male physical competition is common in humans and many other mammals. Wanting to learn how to defend yourself is also perfectly natural. That said, there are reasonable arguments made that professional boxing distorts these natural desires into spectacles where you're enjoying seeing two people inflict slight-but-cumulative neurological damage on each other.
I think along these lines. It's natural for predators (which humans qualify as of course) to use combat, real or threatened, to mark territory, claim a "kill", all that stuff. This is just a refined version of that natural order. Competition too is just an offshoot of the preening of the male of the species. It's still bloodshed, but organized bloodshed with profits to be had, so it passes muster I suppose.
Most of the best heavyweights were actually a bit crazy. There was a quote once by Norman Mailer that went: "It can, in fact, be said that heavyweights are always the most lunatic of prizefighters. The closer a heavyweight comes to the championship, the more natural it is for him to be a little bit insane, secretly insane, because the heavyweight champion of the world is either the toughest man in the world or he is not, but there is a real possibility HE IS. "It is like being the big toe of God. You have nothing to measure yourself by. Lightweights, welterweights, middleweights can all be exceptionally good, fantastically talented, but they are still very much in their place. The best lightweight in the world knows that a middleweight can beat him most nights and the best middleweight in the world will kill him every night. He knows the biggest, strongest man in a bar could handle him by sitting on him. "But the heavyweights never have such simple sanity. Heavyweight champions are alone." You can see that bizarre behavior in recent guys like Tyson Fury and Wilder and Joshua and even Usyk ... even when guys like Joshua try to act mannerly, it comes off as fake. Like he's pretending his politeness is an act. Most guys who were considered the best heavyweight for any period of time (even one night) tended to go off the deep end for a time. It's a heavy burden. Probably one reason why, historically, there weren't a lot of extended reigns at heavyweight. Often guys held it for a fight or two. The people who held it longer were probably REALLY nuts.
It's different when you start as a kid/youth, you're a lunatic anyway at that age, but you see a lot of late starter guys just turn their back and get out the first time they spar and get hit with a clean, hard shot to the face.
It must be incredibly tough starting out, having to train, fight at regular intervals, probably whilst holding down a full time job. That is a love for boxing. Hopefully the rewards come down the line for the chosen very few. It definitely takes a certain type to take up boxing, or any other major contact sport. Sane or otherwise they all have my respect.