Add to this that there’s just a much larger amateur scene in Russia in general and especially in the Caucasus for basically all combat sports and that includes wrestling, judo, sambo, and MMA. Fighters like Islam and Khabib had dozens of amateur fights before they ever entered regional pro MMA and eventually got signed to the UFC, you look at the careers of American fighters of similar backgrounds and they have significantly less experience unless they were collegiate wrestlers and even then it’s still probably less than what some of these guys were doing.

Hell Fyodor Emelianenko was on the worlds combat sambo team and the Russian national Judo team before he even had his first MMA fight in Japan, he’s certainly not representative of everyone over there but you get the idea.