Science shows that people find people that are of a similar level of attractiveness to them more appealing.
A hot guy will think a 7/10 girl is mid, but a 5/10 guy will hard simp for the 6/10 or 7/10 girl.
At the same time, the 5/10 guy will be intimidated by the 9/10 girl and never imagine he could ever get her in the first place, and probably hate the girl more than anything if she actually has a nice personality.
Think about how attractive the average user of twitch and so on are, and their personality.
It makes sense then, that the girls that are super popular on streaming platforms are more likely to be
mid than actually objectively mega attractive.
As a good looking guy, I've never found any of the mid streamer girls interesting at all for example. Only reason I'd consider dating
them in fact is for their money.
Another example I just remembered that demonstrates this phenomenon btw, is think about what type of girl has all the simps hover around them at school/uni etc. It'll be the mid 6.5 or 7/10 slightly nerdy girl the simps think might actually give them a chance, than the clear 8.5/10 girl everybody finds attractive.