>>108652481It's because for male vtubers to work, the target female audience needs to already be able to take to them like a duck to water just based on their aesthetics. But this is impossible for overseas audiences.
Think about it this way: If there didn't already exist a male-dominated overseas audience that was familiar with anime for decades, vtubers wouldn't have taken off. Most of the overseas female audience does not have this corresponding thing to make many of them feel like following male vtubers is "okay".
However, what Japan has in this regard is an incredibly strong fujoshi base, who grew up very comfortable with lusting after male anime characters, shipping them, basically having them in their heads all the time the same way anime-centric watchers grew up thinking about waifus.
I visited Ikebukuro recently, where they have an Animate - the biggest Animate in Japan, in fact - that is completely catered to women. I caught a glimpse of what maybe the people who're pushing male vtubers are thinking about when they imagine a giant fresh market of female fans. It was basically 80% female, the majority ranging from 16-40 years old.
There were girls taking pictures and video of the first-floor screen of male anime idol characters dancing on a flat screen and a giant poster for a BL live adaptation TV drama covering the whole wall of the stairwell.
Imagine a world in which for overseas fans, something like this is mainstream enough to not raise eyebrows when someone wants to air it on TV, even late-night TV. Things like Lycoris Recoil and Witch from Mercury which just hint at things raise eyebrows and commentary on how Japan "doesn't really believe in lesbianism and it's just a phase" or some such while on the other side they just go full on into gay dudes making out. The point is not necessarily that BL is normalized for a female audience, but rather that even if you want to claim BL is a niche, that such a niche thriving is already a sign of how comfortable Japanese women are with, well, appreciating anime male characters. This normalization is what allows vtubers to work, but English-speaking countries simply do not have that.