>>101631063idk about kayfabe, but I think you're right about interest dying without the buff. the thematic/lore stuff is mostly played out by now and while constraints help foster creativity, there's a lot less to work with when so many popular talents dip and take their audiences with them
idolshit market is oversaturated in the west and hololive still has a premium product for people interested in that. loads of indies/small corpos are also trying to pretend streaming and singing/dancing aren't completely unrelated domains of talent, so you can always just find an unrelated 2-3 view if you decide holo isn't for you anymore
and besides *all that,* the industry's been mature for a year or so now so all the easy growth is gone as other anons have mentioned. new growth has to come from existing audiences that certainly already watch a chuuba or three or getting normies to watch. "mai idoru" is no longer a selling point, it's something the average vtuber watcher puts up with so that his oshi's fragile late-20s heart isn't crushed