MMA does have higher barriers to entry in order to succeed. It takes time and resources to train in wrestling, striking, grappling. In Dagestan, they are not cash-rich but are extremely resource wealthy in having people and institutions that offer elite training that is accessible. In places that are not resource wealthy like this one needs to be independently wealthy to fund the training and time to succeed. That and obviously talent, genetics, luck and perseverance.
At least in boxing, the technical training is not nearly as rigorous (although mastery is just as intensive) and far less expensive.