A chess club I played at was frequented by a guy who used to work as mathematician but got fed up by it at some point and started to work as a chess trainer. Still did maths and blogged regularly but never bothered to publish academic work.
There's a lot of people like that in maths. Very talented but dropping in and out of it or doing it recreationally.
I think Grigori Perelman, who solved the Poincare conjecture and declined the Fields medal and Millennium prize money for it, then said he has retired from professional mathematics to avoid the fame, might qualify as the most famous in recent memory.
Interestingly, his seminal papers on (alongside other major contributions) solving the Poincaré conjecture weren't published in a journal but were simply uploaded on arXiv. Moreover, similar to GP's mathematician may say, Grigori quit professional mathematics not just to avoid fame but also due to disappointment over the field ethics.
There's a lot of people like that in maths. Very talented but dropping in and out of it or doing it recreationally.