Bobby Fischer, who some consider the greatest chess player of all time, was World Champion for three years, went nuts, and dropped off the face of the earth.
Garry Kasparov, who many consider the greatest chess player of all time, was World Champion for 15 years, lost to a computer, and delved into the unwindable world of Russian politics.
Emanuel Lasker was World Champion for an astonishing 27 years.
He didn't go nuts. He didn't go into politics. He just took down challenger after challenger. In between matches, he found time for a doctorate in mathematics, authoring a vital algebraic theorem.
Lasker also wrote philosophical books, taught math at universities, became a top-ranked bridge player, published a magazine, and tried to come up with mathematical formulas to beat card games.
Alright, so maybe to do all that, he had to be a little nuts...