MMA is one of the few sports you don't actually have to be good in every discipline to make it to the top, so I'd say it's one of the easiest actually.
I think the real reason MMA doesn't have many young guys who conquer it is because MMA and the UFC by extension have a unique business model, and they need time to sell the audience on the fighters. The NBA doesn't care if a rookie wins a title. The UFC can't allow a guy so young to win a title, they need time to market them and maximize revenue, it's usually never worth the risk/reward to have a young guy lose early on in his career.
In truth, most UFC champions could've been champions at 25-26 but with MMA politics and fighters taking so long between fights, it's usually not feasible on the business side of things. Guys are ducking fights, injuries, dudes taking long layoffs, etc.
The NBA can't wait to have a young 19 year old phenom they can sell for 25 years, but the UFC can't sell a fighter for 25 years, they don't have that kind of shelf life. It's an interesting idea though, but I think there is too much evidence to the contrary. I mean how many UFC champions can we list off right now who clearly weren't very well-rounded fighters but still managed to become champs partly due to UFC favoritism and politics?
Boxing is like chess, a 2000 rated player will never lose to a 700 rated player because the variables are so constrained. You have zero chance of ever beating an elite chess player by happenstance if you're a regular dude. The same way you have zero chance of ever knocking out Mayweather or Canelo in a sanctioned boxing bout, the variables are too confined, and the skill level required is insurmountable.
By contrast MMA has increased variables, creating more unpredictability and giving all fighters a better shot of victory regardless of opponent. I don't care if your Buakow, you can be felled by a fluke elbow or random kick that I didn't even know I was going to throw. This is heighted by the fact MMA is generally a badly officiated mess, things like eye pokes and shots to the back of the head have drastic effects on the outcome of fights. That's not even getting into the fact 4oz gloves completely put the fighters in more sudden danger at all times.
If you just take a look back at UFC history, you'll see that we've had a litany of young champions but that was during a time when the UFC was more intent on giving them opportunities. If young Jon Jones existed in 2024, do you know how many bums they'd have him fight before he got a legit top 15 opponent?? Jon had to fight Stephan Bonnar in his
2nd UFC fight, a Stephan Bonnar who had only lost to current, former, and future UFC champions (Rashad, Lyoto, Griffin). You really had to sink or swim in those days, it was the same for BJ Penn, Frank Mir, GSP, Josh Barnett, and the list goes on and on. Now the business and marketing side is optimized to preserve the youthful talent. It's not that the young fighters are incapable of wrecking shop, Shogun won the
PRIDE MIDDLEWEIGHT GRAND PRIX AT 23 YEARS OLD!!