I was about to do a thread on vtubers, but all the above stuff almost covers it.
To be near the top in streamland you need to be attractive, entertaining, skilled, confident, and maybe be a little bit quirky or fun in your personality.
VTubers are typically people that have no confidence in their appearance or can't handle criticism about their looks, or maybe they look good they are just lazy and don't want to spend an hour a day on it. Alot of them crawl out of bed at degen hours and just fire up their stream in their pajamas. You can only really tell when they play something active like ring fit
Skillwise I've yet to see one near the top of any game. Some are absolutely terrible at anything they play and half the fun is watching them fail and make angry anime noises. The only impressive thing I've seen is Gura doing some pretty amazing speedrun stuff in a 2D game.
The "companies" that own alot of these girls are all very different. They often form relationships with developers and get permission before streaming. Probably some money changes hands since a really huge amount of eyes are on them, but also some publishers are really cunty about streaming like rockstar / nintendo.
The japanese orgs mostly want their girls to be "idols". This goes beyond being able to sing and draw, there's a really strange set of rules they have to follow. Idol culture is one bit I can't even begin to understand, but again hiding behind an anime character helps them alot with some of this. They can go out with friends on the weekends and not get followed by the paps.
The non Japanese orgs like vshojo seem to be more wild west whatever. Vei can get super foul and dirty and has often laughed at the idol side of things, even taking aim at hololive and the way they control and own all the characters and such. As a result collabs between the two sides are rare. There was one recently with Kiara of Hololive and Nyanners of vshojo.
The more successful ones just have a nonstop torrent, buckets filled with cash raining down on them at all times. They can't even stop to notice the donators or that would be all they ever do. Typically they will do a several hour show on sunday where they go back over the week's donations and thank them all as rapidly as possible.