At least in the cases described by the author, the comedowns weren't because the world didn't care about if they won or lost - or if they got the release or not (or monetary reward).
The comedown was about the loss of structure, degree of control, and clarity of goals.
It's analogous to what I hear from many people (including in my head) when you finally get out of school into the real world. It's also (based on what I've read and heard - I certainly have no first hand experience), analogous to something that many veterans feel going into the "real world".
The structure, clarity of purpose, knowing that everyone has more or less the same goals, knowing that you have non-trivial control to advance yourself towards your goal (winning gold, getting the grade, surviving the deployment, etc) which you know no-one will question.
We live our normal lives never quite sure if we're trying to do aim for the right things, and never quite sure if we're doing it the right way. We spend our whole adult lives coping (and perhaps thriving) with that uncertainty. Some of us fantasize about "more simple" lives, ultimately because the reduction in choices and things to consider mean we can (hopefully) go about our lives with greater clarity.
I don't know if "the real world" could be any other way. But perhaps on some level, we keep pushing people along this "bad career" (I don't think it's bad really... but that's a different discussion) because we all on some level want to believe that that idyllic, focused life can exist.