Most guys who lose a MMA world title fight decline shortly thereafter. On the way to the title shot, they're usually on a roll, & feel like a worldbeater. Then losing to the champ is a reality check, like "you're not good enough". When you lose before ever getting a world title shot, you chalk it up to "I can still get better, I'm still green", but when you lose a world title fight, your skills have realistically hit a plateau at that point, you were already basically as good as you're ever going to be.
Confidence is a huge thing, once you lose it it's hard to get back the mojo. There are exceptions of course, but if you look at the records of guys right after losing a MMA world title fight, most of them afterwards have much much much lower winning percentage, many go less than .500 afterwards
