Brock, Cain and Jones became champs with only a few years of training. You know nothing about Boxing. It is so much harder to reach the top then MMA and its not even close
The sheer amount of tiers boxing has instituted from golden gloves to the big 4 pretty much guarantees that you will be put to the test at some point.
MMA is much less linear, so you'll get the odd phenom with less than 10 fights that can climb quickly and win a belt.
But then, that moment that boxing would have forced you to deal with on the way up, comes for a guy like Chris in the form of a 3 fight skid all stoppage losses, with no clear answer to going back and fleshing your skills out retroactively since your confidence has been crushed so completely.
MMA probably has the most ways to win but lots of safe places if you're grappling and running game, whereas boxing has 4 corners, 8-12 rounds and no chance for ride time to recover while staying safe.
Boxing is like being a competition shooter, your doing one thing exceptionally well and a fraction off is devastating to you bc everyone's trying to sharpshoot.
MMA is like a prison fight, where lesser men can benefit from chaotic exchanges and find one of the 4 types of stoppage (choke out, knock out, broken limbs, TKO flurry) that we see typically. Many ways to lose and many ways to win.
Boxing has lots of areas where you can tax a lesser fighter and at the world level, that's what decides fights. But if you've ever been boxed up, you know how hard it is to box better after the better boxer has established the pace and is going to work on you.
It's like being overwhelmed while seeing it happening and being unable to defend.
If you're the better boxer, you'll win most of the time. If you're not the better boxer, you won't suddenly start doing shit better after being punched and cornered. The gap continues to widen.
In MMA, you can be firing on all cylinders and get snagged by the heel and it's over.
No gap big enough to be truly foolproof, so it's a mix of handling variables while dishing out damage. But the race can end anywhere along the way and the better guy doesn't necessarily win as consistently and assuredly as the better boxer does.
But there's a clear difference in the way MMA 'builds' fighters just to throw them in the deep end too soon.
Boxing is a better system for longevity and craft
MMA is comprised of multiple areas where a guy like Brock may be better in 1 out of 7 areas, but his 1 was enough to smash Mir out despite the gap.