>>149388618 (OP)
Because it is their "sport". Wrestling to the Caucasus is like what soccer is to South Americans, or Track is to Jamaicans, or Table Tennis is to Chinese, or what American Football is to Americans. In the Caucasus, particularly Dagestan, wrestlers and MMA fighters are their celebrities. They are the ones on billboards and driving around in Range Rovers. Kyle Snyder went to Dagestan to visit Sadulaev a few years ago, and said that more people recognized him halfway around the world than they did in his home town. They simply care about it more, and it is very well financed. There is virtually no money in being an amateur wrester in the west. I remember either Islam or Khabib one time saying that in Dagestan, wrestling gyms almost served as daycares, and it exposes lots of people to wrestling at a very young age. The no drugs no alcohol no women things probably helps with eliminating distractions, too.
tld: cultural reasons, better infrastructure and state support