They often can't delete everything because they have lost track of their passwords and emails for old, unused accounts. Even then there's often archives. They should be able to just private their personal accounts and use them normally, but if you've got dumshit friends posting replies to your vtuber stuff and also still tagging you in their posts.... well they should stop doing that!
It does make me wonder if there's more to it, like if she had directly confided information to the "super duper fans" or started some personal communications and they're trying to get around that. Otherwise it's making a mountain out of a mole hill, but i guess that's your point, it makes people not talk about the companies other fuck ups.