Non-sumo combat sports are very popular in Japan among young people, and pro wrestling (if it can be considered a sport) has broad all-ages appeal there. Not anywhere close to baseball or soccer, but definitely not obscure either. Sumo is always cited as a top sport, but I read that the median age of sumo fans is close to 55. Even though it's part sport and part art & cultural, it isn't really connecting with the younger audiences to carry the sport forward in the future.
Mass appeal isn't needed for athletes to find world-level success, but local popularity of a sport obviously has an exponential effect. A pretty good case study for wrestling might be the popularity of Judo in France. French fans are impressively fluent in the sport. And so many parents send their kids to Judo lessons because they believe it's a necessary part of their childhood education alongside academics, arts, etiquette, and other physical exercise. There are clubs everywhere. I don't fully understand how the sport became so engrained in French culture, but I would love to see it emulated in wrestling.