Node was the best choice for our service, I'm willing to go to court with this. We need a fast fire and forget server to talk with Redis continuously, what's a better option? Erlang? I think there are ~3.6 developers in Israel that know Erlang.
This phrase actually captures, succinctly, a big reason for Node's success: If you decide not to use a JavaScript-based tool you have to decide what to use instead. The ensuing debate will often take three times longer than just using Node.
Everyone who touches the web needs to know JavaScript, so apart from any other consideration there's an automatic tendency to try the thing that's written in JavaScript before trying anything else.