>>1204499Change in VTuber culture.
The initial VTubers were all Seiso type idols. Tokino Sora was essentially created for that era.
Mito was one of the early ones that started shifting the culture from idol to comedian (I think the first one was Kaguya Luna) and many of the vtubers that followed her contributed to that cultural shift (as well as desire by the audience).
Ironically people like Fubuki, Marine and Korone have more in common with Mito, than they do with Sora.
That being said you are heavily underestimating Sora's success. First and foremost I want you to look at this video
https://youtu.be/OXW-_3w7dc8Notice that Sora was the most subscribed Hololive for two years. Two years. Without counting the Nico Nico numbers.
Second thing to consider is that the Idol VTuber is basically dead, everyone who used to do that schtick is either gone or has transition into more of a comedian type content (Kizuna AI for example). Sora is still standing.
Lastly Sora never declined, the other girls have had more expolisve starts and much better growing rates, but Sora has been going slow and stable since 2017.
