Guts of it is that Neovim didn't play nicely with their OCaml build and Vim did. Rather than invest time in working through the problem, they went ahead with Vim but remain open to supporting Neovim.
I don't think this is a fair characterization. We've made significant investments in both Neovim and Vim, and carefully considered the trade-offs.
> Guts of it is that Neovim didn't play nicely with their OCaml build and Vim did
This was a smaller consideration - but more fundamentally, the model Neovim uses for input - queuing it on an event loop and handling it asynchronously - is at odds with what we required - to be able to process the input -> handle updates synchronously.
There was a significant amount of incidental complexity in the architecture of our V1 to fit that asynchronous model - we wanted to avoid that for V2, and we switched to Vim because it fit that model.
I think the link summed it up well, near the end
> this was purely a constraint-based technical decision