It's still absolutely baffling to me that anyone is willing to run JS server side. There are so many options which are much better suited, why are people willing to jam that square peg into the round hole?

Perhaps the siren song of "isomorphic JS", where you can run the same code on the server and on the client? I can see the use case for having complex model and validation code running on the client for speedy feedback and on the server for security, and perhaps also the idea you could render something entirely on the server when needed (eg for indexing and non-JS clients) and on the client when it's capable.

Personally, I wouldn't want to touch server-side JS with a 10 foot barge pole.

Because they don't know and don't want to know anything else. Not a single polyglot developer I personally know have ever chosen JS for server side, not once.

There was something long ago called GWT -- Google Web Toolkit -- that tried to make Java into that language by having it compile to JavaScript.

It actually worked decently well, but was due to Java needlessly verbose.

WASM lets us run other languages efficiently in the browser but that just opens the field to a lot of languages, not one language to rule them all.

Also GWT apps were pretty slow to load and start, and were very "app"-like as opposed to web-page like at a time when that was not as familiar as it is today. That's how I remember it anyway. And pretty heavy, developer wise, at a time when "update a file on the FTP" was still normal.