It's clearly allowed, but I think the reaction here is negative because, unlike for example Python, this isn't someone making their own language from scratch which is then organically adopted. Instead, it's essentially someone looking at an established language and community, and saying "you'd all be better off if I was running the show here." And the person making that claim does not have the track record to make that claim believable. I don't think it's strange that people are reacting with some reservations here.

Of course it's not a hostile takeover, he'll try to build something that convinces people that he's on the right track, and I wish him the best of luck with that. There's a small chance that the project succeeds and essentially becomes the successor language to Haskell, and there's a large chance that the project fizzles out, and both of those outcomes are fine. The worst possible outcome is that it succeeds well enough to fragment the ecosystem, but not enough to really take over.