PVZ is awesome at marketing.
If want to show the contrast of WMMA to impress people -- super feminine ass kickers is the selling point -- you don't do it by being just another grumpy female fighter showing how masculine you are. You show up to the conference in a damn sundress! You wave to the crowd and have a good time. You do your hair before hand. You get people to say, "really her? she's a fighter?" then you rock it in the ring. Rousey is uncomfortable with this role but is trying and it sells.
Herrig being the anti-PVZ and reactionary just enhances PVZ appeal.