That's like saying it's harder to be a popular basketball player or a boxer if you're white
Come on man, let's not make an argument out of something that does not exist. I'm not denying the existence of racism, but being non-white or white has nothing to do with one's popularity in MMA. It's all based on how good the fighter is, fighting style, and personality.
Mighty Mouse's issue is mostly the lack of interest in that weight class, but what hurts him even more is the lack of big names he's facing. The last guy he fought that I was actually familiar with was Dodson, and this was 4 fights ago. This is why it was a shame that the fight with Dillishaw didn't happen, I think it would have put him on the map had he won it.
All the other guys you posted either fought well known competition and have done well, or they're huge personalities.