Why do nearly all serious, hardcore women bodybuilders have....?

Yes, it's either the testosterone or it just looks bigger because the usual cushion of fat on the vagina is gone, so it's protruding.

Dude, how many have you seen naked? And why?

Female Bodybuilders Vagina

And you've seen how many hardcore women bodybuilder's vaginas??? *shakes head* If it's that repulsive to you, why are you hanging around them when they're naked and exposed???

Women cannot naturally bulk up so consider whatever they are taking to help out, is likely to have other effects...