V-tubers are fictional characters.
They can just say that the vtuber got isekaided and can't interact with earth anymore.
Then they can still keep selling merch based on the design.

Also hire mangakas to create more stories with the said vtubers, just to release more content.

Transform the v-tuber into an anime character.

Imagine if Goku's VA died, they would still keep doing more stuff with Goku.