Microsoft has the resources and ability to make better language servers which could be closed source now, so people end up switching to those tools, owned by Microsoft, with better language servers, killing other editors if they are not able to catch up.
E.g.: Why would a C# programmer use Neovim if the language server is worse than the one that VSCode has? (Which is now proprietary and closed-source). The difference right now is insignificant, but the future tools and features that they are adding to the new proprietary C# language server will not be available for other editors.
[1] https://en.wikipedia.org/wiki/Embrace,_extend,_and_extinguis...