TITLE: Examples of mathematicians who lost interest in Math and got interested again?
QUESTION [31 upvotes]: I am looking for some examples, and hopefully some short biographies on mathematicians who lost interest in Math along the way, and somehow got rejuvenated again. (Better still, who managed to do something interesting)
I hope to gather these examples to encourage myself. Any help would be very much appreciated. Thanks!

REPLY [4 votes]: It's not 100% clear that Grothendieck lost interest in mathematics, but it seems that he didn't make any mathematical research during almost the whole 1970's.
He began to release mathematical research papers in early 1980's.
From Wikipedia:

After leaving the IHÉS, Grothendieck became a temporary professor at Collège de France for two years. A permanent position became open at the end of his tenure, but the application Grothendieck submitted made it clear that he had no plans to continue his mathematical research. The position was given to Jacques Tits.
He then went to Université de Montpellier, where he became increasingly estranged from the mathematical community. Around this time, he founded a group called Survivre, which was dedicated to antimilitary and ecological issues. His mathematical career, for the most part, ended when he left the IHÉS.