Several Olympic athletes in these Games who have already won championships and Olympic medals are not living up to the expectations.

I think you may be right that cracks were already showing. I watched the track and field qualifying and all they talked about in the 400 was the reigning World Champion. He got smoked - finished 5th or 6th. Then I read he hadn't run a time within a second and a half of his pr in two years. Well hello! I wonder how many of these athletes who are "failing' haven't demonstrated peak performance leading up to the Olympics. Osaka took two or three months off for a mental health break.

Obviously pressure is a factor, but confidence is more important to the more experienced athletes. It seems like if there is a twinge of doubt, they become very fragile or otherwise are not in peak competitive condition.