To be clear, this was developing software running on *nix environments, and they were all using Mac (or WSL) and the usual open-source *nix dev tools. This is not a case of developers purely targeting Microsoft environments (indeed it would be excusable in that case).

I am, although I have used nix occasionally.

In Europe C# fills the role of Java.

You're just in an American echo chamber.

Now the number of senior C# engineers in Europe who couldn't fix a broken deploy on IIS or SSL cert problem on a windows server? That is rather high in the windows field too.