>>27662474No one really knows who's blocking it, but this my personal theory.
Holo probably sees NijiEN as a threat. In my opinion, the nijiEN girls (nijisanji in general) are more entertaining, and funnier than the holoEN. Hololive's management doesn't wanna give them any exposure and risk their en male audience flocking to nijien girls. NijiEN girls are still smaller HoloEN girls, and holo's management would prefer to keep that way..
The other niji branches (i.e. nijiID and nijiJP) already had history of collabing with hololive before holoEN existed. I'm assuming they got grandfathered in.
My personal rrat for why Astel and Reimu haven't been allowed to collab, is so that Kiara wont complain about her not being able to collab with Pomu. Hence the company wide collab ban. Maybe they'll change and start allowing collabs with NijiEN, if holostars ever becomes any more desperate for exposure. Sorry if that sounded harsh.