How else would you explain the moves well below his level that objectively cost him? He is a great player but does not have Magnus’ mental and emotional consistency. Not everyone advances to the top in chess with the same combination of inner traits. This is also seen in other competitions where humans must perform at their absolute best in all aspects to reliably win.

Saying Nepo has less mental endurance than Carlsen is not the same as saying he doesn't have any as this poster wrote.

Ah. I think the meaning was clearly relative to the level of play and you took it too literally.

That’s incorrect. The original poster said Nepo lacks the mental endurance required to be world champion, not that he lacks it altogether.

He lacks enough of it to become one at this point in time (when we have Magnus and Nepo has his current mental edurance) :)

Actually relative strength is one of the things that wonder me the most I would say in the game: when one of the opponents is much stronger than the other the wins look so easy and the loses so stupid, but when the winner is matched against someone even stronger you see the same exact picture. I love you all I dunno why I say that now but here you go.

Before the match, Carlsen said about Nepo:

“It remains to be seen, of course, if Ian will be more resilient than he has been in the past if he is down”

So yes, it seems he has a bit of a problem in that department.

(https://www.theguardian.com/sport/2021/nov/24/magnus-carlsen...)