I don't know anything about Kolmogorov, so I can't evaluate the assumption that he obviously saw through the lies and was horrified by the brutality - but I will note that a great number of prominent intellectuals, who were in absolutely no private danger from the soviet regime whatever they'd believe and say, and who definitely had access to information about the brutality, who still chose to support and defend the regime.
Without evidence to the contrary, it's plausible that Kolmogorov simply supported his government and found the brutality to be acceptable collateral damage.
If we've learned anything from the 20th century, one thing should be the lesson that even very smart people can be found supporting extreme brutality in support of an ideology.
I wondered the same thing, there is an excellent book on this topic called "The reckless mind" that might interest you if you didn't already read it. I portrays great thinkers who got swayed by totalitarian systems and asks why.
I'm going to preface this by saying that I'm not remotely comparing the two situations, but a whole lot of people in the us stood by and watched us launch a pointless war of aggression based on lies that we're still seeing the bloody consequences of today.
This is not about being wrong or not resisting -- everybody can be wrong. The contemporary equivalent would be the Neo-Con intellectual who still today defends the invasion, who goes to Baghdad and sends back rosy reports of how healthy Capitalist markets are providing plentiful goods and well-paying jobs to all and the swift eradication of poverty in Liberal-Democratic Iraq, and who angrily dismiss all arguments that things are actually pretty crap by blaming the state of things on the existential and entirely justified need to fight Iran-funded insurgencies and the damn communist Kurds stealing the oil in the north.
Related, I was shocked to learn just how popular Soviet ideology was with western intellectuals in early- and mid-XX century, even though there was already plenty of evidence available about how huge a disaster it was.
We're not talking about hindsight. The people who got excited in the 30s, then backed away, are easy to forgive.
We're talking about people supporting soviet communism literally for decades after the evidence for the brutality required to sustain it was incontrovertible.
It's about the hindsight from your and my perspective, today.
Think about it: in another few decades people may (or may not) look back and wonder how intellectuals could support the system we have today despite of all the bad things happening.
Without evidence to the contrary, it's plausible that Kolmogorov simply supported his government and found the brutality to be acceptable collateral damage.
If we've learned anything from the 20th century, one thing should be the lesson that even very smart people can be found supporting extreme brutality in support of an ideology.