You have to remember that they view attractive men and unattractive men in completely different contexts
Attractive:
>he's so much more capable than me, our kids would be perfect, i'll do whatever I think will make him commit to raising a baby with me
>he's so genetically fit that anything he likes or does must be good, i'll let him shit on my chest and hit me
>he said he doesn't like girls with long blonde hair, i'll try to match his celebrity crush's haircut
>anything to keep him with me
Unattractive:
>god he's so ugly, our kids would fucking die right away, even if he's more capable than me I need to try to undermine him so I don't risk letting him reproduce
>he's so genetically unfit that anything he likes or does must be bad, i'll call ridicule him with my friends if he talks to me
>he said that girls who get buccal fat removal and spray tans look ghoulish, I'd better do both of those things so that only Chad will be attracted to me
Obviously they're not literally thinking these things, it's far more convoluted (which is why most girls don't even know why they like the guys they do).

But that's the streamlined version of why they do this shit: Generally, only unattractive guys even have these conversations within earshot/in online spaces visible to women. Attractive guys also don't really have to get into a deeper conversation with a girl to get any play, so the things they find unattractive never even come up, so these girls just assume that they're really hot after doing this.

There's also a solid argument for intra-sexual competition. Bodybuilders aren't attractive at all, but unless you're LARPing you're absolutely a little physically intimidated by them (inb4: "nuh uh i do Fist of the Faggot and I know I'd win). Similarly, girls absolutely seem to think this shit is pretty, so it's a way of achieving status among other women. If you don't compete intra-sexually as a girl, you can be ousted from the group and you won't be getting with hot guys anyway.