>>9458216Entertainment in general and vtubing specifically doesn't really attract "smart" people in the first place. Not saying they don't exist, but they're so rare that being recognized as a "smart" chuuba is almost a character trait in itself. Actual intelligent people mostly gravitate towards other professions, and the people who want to be entertainers (of which vtubing, due to its low barrier of entry, is basically bottom of the barrel -tier) do it for other reasons (mostly has to do with wanting attention, etc.)
Many of the girls also have comparatively low formal schooling (again, because it's not necessary for vtubing, and/or vtubing is an escape because they can't get better "real" jobs anyways with their low education level).
Also remember that even if they aren't just genuinely dumb, at least some are also "playing dumber" than they probably really are. Ahos and bakas are a popular anime girl character type, and for good reasons, it just werks (is an easy source of comedy, is "cute", gets simps to go "d'aww" and throw money at you).
As for your question about foreign language ability specifically (the discussion if that's really a sign of "intelligence" nonwithstanding), well that's a general Japan problem, not just vtubers (hell, the average vtuber probably even has better english ability than the average random jap on the street, even if just because they have to deal with EOPs shitting up their chats etc.). Japans english teaching is famously bad and so ineffective, you'd have to think it's almost by design. Unless the person is actually interested in western things and motivated to self-study, he/she will not come out of 12+ years of school with any conversational english ability, and for most people they're fine with that, because learning english is mendokusai and they don't really need it in their day-to-day life anyway, they're a rich first-world country where the average person can afford to only speak their domestic language and never feel any disadvantages for it.
