there's a difference between media obligations and and "self promotion" of MMA, they might as well be a different thing all together. traditional sports media are pretty tame, it's usually a bunch of run of the mill questions about the game, the players are taught to give PR answers, there's usually never any drama unless specific reporters who are known to ask dumb questions show up. Or if someone like Popovich decides give reporters are hard time for laughs. There's little to no trash talk at all between teams.
Self promotion is combat sports does play a role, but it was never necessary. It's a 100% the promoters job. For example I have no idea what Canelo and GGG sounds like, they don't even speak much English, yet I still bought he PPV being a non boxing fan because they convinced me it was like fight of the year. When you look at the history of combat sports, there are popular fighters who talks a lot of shit, there are also popular fighters who didn't peep out a word. Ever since Conor people have this weird idea that you have to act like him in order to be popular, and fighters MUST self promote. Did Fedor talk shit, not really, what about GSP, not really, yet they were immensely popular.
by the way outside of combat sports self promotion is not important in traditional individual sports either. Tennis is a prime example, Federer is like one of the most popular of all time, but he never gives out anything but PR answers in interview, what about Nadal, he barely speaks English and never says anything controversial either. What about Tiger Woods, what did he do to self promote but just play really great golf.