Wrong question. Question should be why couldn't he handle his first loss. Same with Tyson Fury. Both are mental cases who couldn't handle their first loss. Usyk did to Fury what Fury did to Wilder. Both got their hearts ripped out and ran away from Boxing Naseem Hamed style. Only difference is wilder accepted his limitations and handled his subsequent losses better. Fury is still in denial and refuses to accept his losses to Usyk. He's basically still in Wilder 1 and 2 mode.
A combination of getting older and fighting better opponents. Even in his prime he likely loses to Parker and Zhang, although he would have a reasonable chance.
He dropped fury plenty of times, some very heavy. Fury doesn’t conveniently stand still. usyk is a different maze all together but the theory that wilder only catches statues isn’t true….
Same as with many (most?) highly protected fighters who keep their zero much longer than they should... They get to feel invincible, it becomes a fact and an integral part of their identities. A long undefeated fighter getting back into the ring is like a priest who's realized there's no God getting back into the pulpit - only the very finest bullshitters are going to be convincing. In fairness to Hamed, he was physically destroyed before Barrera... The timing of the loss just made it pointless to pretend anymore. That said - you're not wrong with the parallels. I guess the other big difference is that Wilder's subsequent losses to Parker and Zhang were so completely one-sided that even the most delusional of fighters couldn't deny it... Fury could fool himself that the Usyk fights were competitive enough that he might've won (they were clear losses, but the first at least wasn't a completely one-sided demolition).
Mix of leaving a lot of himself in the ring in valiant but brutal beat downs, losing the force of that indomitable bronze bomber aura against Fury and fighting tough opposition in the aftermath of that trilogy. He fought Helenius who is basically a punching bag at the top level, he did one single round, then fought Zhang and Parker, who are basically A- in the division the rung below elite. Stupid matchmaking. Or maybe Fury taught Zhang and Parker how to smuggle egg weights inside their gloves whilst being watched having their hands wrapped by someone from team Wilder.
Fury gets KD in half his fights so that means nothing. Wilder's power looked good versus mid tier opponents. The day he stepped up was the end. ZOMZZZ ZQSAUZSD
If Ortiz had 10 seconds left in the 7th round of their first fight he would have knocked Wilder out, he was near unconscious standing up, he was never a good fighter.
In descending order of contribution: Simply exposed...fighting better competition Regressed by firing Breland Got old Badly damaged in the Fury fights Big gap between 1 & 2, and 2 & 3, very small gap between 3 & 4.
Not being able to fire the right hand is definitely down to 3-4 more than anything else. That's not to say he would have necessarily beaten Parker and Zhang beforehand..... But he definitely wouldn't have labored with that journeyman for 7 rounds.