>>23126010 (OP)
Unironically inbreeding + eugenics. That and the nature of the region. Basically the Caucasus peoples are heavily inbred not even so much due to Islam, but due to the isolation that is naturally brought about by the geography for thousands of years. However, because the region requires such rough living because of Spartan conditions, all the negative effects of inbreeding have been routed out. There are towers in the number of dozens even in small villages due to the militance of the region. Due to scarcity, war, harsh climate. All retards and genetic freaks died off. Only those who could simultaneously inbreed but were also not disproportionately predisposed to passing down negative traits would survive and breed. This is a common phenomenon in isolated populations. This is why the North Sentinelese don’t die off despite millennia of genetic isolation.
Anyways Caucasian kids were poor and already had a martial history so their conservative culture, poverty, boredom and need for national pride drove them to obsess over MMA from a young age in the post-Soviet era and due to aforementioned reasons they have retard strength without any of the downsides of actual retardation due to their unique inbreeding circumstances