It looks to me like chess is an excellent way to learn a rare and important part of rationality, but becoming a chess grandmaster is a terribly irrational life decision for almost everyone due to the intense competition and low rewards. Also, at world champion levels, many skills, especially intellectual skills, probably rely on biological abnormalities which correlate highly with autism, psychosis, etc. Also, extreme privilege and fame, especially at a young age, is very often a cause of functional insanity. I suspect that this includes the privilege of growing up with modern 'magical and opaque' technologies.