Like others are saying, which I took for granted, she was affiliated with Hololive. I think that's just it. They're insanely popular and have a huge audience, even back when they debuted they had a large audience comparatively.
Another thing to keep in mind, vtubers have had a huge boom in recent years. Rushia debuted 2019. It wasn't until covid hit hard that vtubing took off both in Japan and in the west. Back when she gained her audience, she was the only "famous" one with that content and she was one in a million when it came to her GFE content. But why she didn't gain as much attention when she came back in another form, I have no idea. I know too little about the japanese hololive fanbase.
There's a clip when a japanese fandead hears about Rushia having been married during her last years as Rushia and he goes literally insane with grief and anger. Definitely check out some clips of the golden days.
