Maybe he realized that while you can win at playing chess, there is no ultimate solution to chess - it is an endless rabbit hole (you come out the other side somewhere around China).
Like tic-tac-toe, it is now certain that perfect play in checkers always results in a draw. It is suspected that chess is the same, although white has a significant advantage if black makes a small mistake. Against computers, humans can no longer come close to winning. Against another human, or wristwatch sized computer, the game can still be fun. But in the end, it's all just a big waste of time. Very little learned in chess is useful in life.