I do very much like a video from ages ago, where two women have fought, one of them by her own admission in the interview said (and at this point I'd like to add, I love it when a fight is humanized by us getting to know the fighters) that she's a girl next door type who's never been in a fight, but was interested in the financial compensation, and she had seen some videos before, so I definitely think advertisement is one angle. I love it when back in the day it was framed as "nonsexual erotic work", since it's still an adult video.
The other woman had been in fights before, one of them had to be broken up by a deputy. As far as I know, arrests record, if the person isn't underage or it's sealed by a court, is public knowledge. I'm not saying they had a lawyer or cop friend to find them spitfires who have had troubles with the law, but it's not improbable either.
Last, but not least, I do know that Eastern European women are attracted to this for one or two reasons. The first one is, that outside some music festivals, there is no oil and mud wrestling scene, strip clubs don't offer them, and contact sports aren't sexualized, there's just straight wrestling or kickboxing. You don't have to take my word for it, a lack of sexual revolution is a strong indicator if there's no public interest, there's no commercial supply either. There, however, can also be a secondary reason. Some get involved because they like the sensual side of wrestling, to mean they're LGBT. Now, being LGBT isn't that much welcome (it's practically legal to deny lease to an apartment) so it's easier to build a career in fighting sports where people are more appreciative of what you are and who you are.