Gura was a major factor in popularizing singing in Hololive, from her debut and her unarchived karaokes, bringing in 200k live viewers.
Anons forget that Cover's singing branches were flops, and even Suisei didn't get popular until much later, after switching to Hololive. Though record labels help.

It's not the ability to mimic a song, but adding their own flair, arguably better than the original.