A while ago, Scott Aaronson wrote about Kolmogorov’s way of dealing with life in a Stalinist paradise. He mentions how Kolmogorov testified against his former mentor Luzin. It is suggested that Kolmogorov was blackmailed into doing this by the secret police, who threatened to reveal Kolmogorov’s homosexuality.
But that’s silly. It is based on the assumption that Stalin’s agents needed a reason to put you in the jug, send you to Siberia, or kill you. If you kept your nose clean, obeyed the written and unwritten rules, nothing bad could happen to you! Because that would be wrong !
The firmament of the Soviet Union during the Great Purge was studded with dead stars. No one was safe, no one was innocent. Old Bolshies, creative artists, four-star generals, farmers with a cow, ex-heads of the Cheka, personal friends of Stalin serving in the Politburo – nothing made you immune.
Supreme talent in a profession with military applications gave better-than-average protection: there were some scientists that, as far as we know, never informed on anyone. I’ve never heard that Kapitsa did.
That was probably more the case after the Bomb, when the survival and success of the state hinged on nuclear physics, and they really had to put up with people like Sakharov.
Kolmogorov was a hell of a mathematician, but not a particularly admirable man.