>>90942054A-Chan retiring was completely normal. I know you don't follow Hololive but A-Chan was absent for a long time before she quit. She had a replacement hired and running the show long before she left. The only thing weird about it is she's not a vtuber but a higher-up in the company so you kinda have to assume she still has some role somewhere in there or actually could return in a way the normal talents actually can't. She knows too much to actually be cut off, surely.
Someone like Miko abruptly quitting and abandoning all the goals they've been working to for years would be bizarre and impossible for any fans to believe because it's a contradiction to everything she's ever said or done. Every graduation this year has been predictable, even the termination to be honest wouldn't have been shocking if it was a graduation instead.