Technically, Neovim started because the author wanted to add multi-threading to Vim but the patch was rejected. So they did try to contribuir to Vim first.
Not that I agree with your parent comment or anything (I don’t), I use Helix so don’t really have a dog in this fight, I think it’s fine for them all to coexist.
And did so in its (or rather Bram's) own, incompatible with Neovim way. I imagine that's the biggest problem with Vim why Neovim was even created - hardcore NIH syndrome of Vim's main author.