If you're in shape you're in shape, there's no critical moments. You either have the legs or don't. He just isn't good enough for those two guys, it's that simple.
Mental thing would be if he somehow made a mistake, could follow but didn't, or something like that, rode too much conservative, or vice-versa. But no, he didn't have tactical mistakes, he just physically couldn't follow Van Der Poel and Pogacar.
Look at Valverde for example, he had some mental things in biggest races, often rode too conservative and made some mistakes that cost him some big wins, Lombardia 2014 and Worlds 2013 comes to mind...
And Tour, he needs to understand that Tour isn't the race that will define his career. It's nice when you're strong there, collecting stage wins, making some great performances, but he's a classics guy, just look at how big classics riders of the near past treated that race: Museeuw, Bartoli, Bettini, Freire, Boonen, Cancellara, Gilbert...
He's an exceptional rider, no doubt about that, but right now it seems to me that he's half a step below the very best, at least in classics.