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.

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.