Comparing this to Stalin's purges is borderline offensive. The latter's purge affected almost all walks of society. I recall when I was in grad school I would read the biographies of famous physicists/mathematicians, and virtually all the Soviet ones had siblings or parents who had been killed in the Purge.
It also crippled the Soviet army, which is why a much "weaker" Finland held its own when the Soviets attacked them - the majority of the senior, capable military leaders had either been killed or imprisoned in the Purge, leaving behind a rather incompetent military.
It’s also borderline offensive to treat Putin’s regime as anywhere near as transparent about how people from all walks of society are treated. Famous scientists and mathematicians just mysteriously fall from windows with no apparent explanation. People less famous either meet less notable ends or just aren’t there to be purged from anything worth purging in the first place.
None of which is to say Putin’s regime is anywhere near the atrocity machine that Stalin’s was. That’s an extreme that’s hard to imagine and very exclusive. But this notion that Putin’s regime isn’t committing the kinds of mass violence on Russian society because it isn’t on full display is neglecting both how his own regime has operated as well as how most did/have since the 70s-80s. They just do it with secrecy and plausible deniability.
Just from the top of my head I recall 3 healthcare workers (was it doctors?) that have been critical of the national Covid response who fell from windows. A diplomat in the russian embassy in Berlin. More than one journalist¹ — the only reason there might be no mathematician recently might be that the soviet union had a bigger use for methematicians.
It also crippled the Soviet army, which is why a much "weaker" Finland held its own when the Soviets attacked them - the majority of the senior, capable military leaders had either been killed or imprisoned in the Purge, leaving behind a rather incompetent military.