Money is money. And there's more of it in Iowa than in New Mexico. Individual Iowans have more of it than individual New Mexicans, and the state of Iowa has more money running through its economy than does the state of New Mexico.
Seed money for something as small as a MMA gym can come from anywhere at anytime and go to any place.
Albuquerque is larger than Des Moines or Cedar Rapids, but I doubt that has much of an impact on funding for MMA gyms. It's probably a simple and better explanation to say that fighters find Albuquerque more attractive because they can get elevation training in milder winters than would fighters training in Iowa.