I wonder how deep wrestling/grappling sports actually is over there? It could just be that they have a great program, and they do everything they can for the handful of kids they do get to get them to the top. But that does not mean they are extremely deep.
Like for example, my homestate of New Jersey. We produce lots of great wrestlers (HS rules) for a tiny state. But most kids in NJ are not thinking about wrestling. They care more about FB, BBall, hockey, Baseball, even soccer, tennis blah blah blah. But we have really good wrestling programs like Blair Academy, and that props kids up and sets them on the path to achievement.
So what are most kids in the Caucasus region dreaming about? If most kids really arent into wrestling, then I dont think there is anything genetic or cultural about their success.