https://en.wikipedia.org/wiki/Ettore_Majorana
Majorana basically disappeared in 1938. It has been suggested that he could see the feasibility of weapons using fission (Leonardo Sciascia wrote a play about this). Opinions vary and the issue is cloudy and ripe for fiction.
That was interesting read, thank you. I wonder what his stance would be after experiencing nazi extermination camps, people often flock to populists promising cleanup of some non-ideal situation but what it actually means down the line is far more sinister (or just empty words like mexican wall which could be completed for years if wanted).