Using non-blocking IO is a very old trick. Even nginx does exactly this, and it's written in C. The ability to use non-blocking IO does not make a language unique in any real fashion.
However, I guess what made it appealing initially, was that it uses a syntax known to a lot of web developers. The callback pattern helped.
Although these days, we have been moving away to generators or async-await.
This is the key. And it reflects poorly on them for that. Syntax is the easiest part of a language to learn. The nuances of behavior is the hard part - and those nuances change as you move from the browser to the server; what makes good browser code will not make good server code.
In reality they shunned a ton of knowledge and community support to keep a particular (and particularly mediocre) syntax. Even today, years after Node has reached popularity and many lessons have been learned, developers with no experience outside the browser think they can write perfectly good server code, simply because they know the syntax. Never mind that all of the design patterns change. Never mind that the core libraries they use change. Never mind that they suddenly have to be cognizant of how much CPU time their code takes.
This is really true and it's sad, because it leads to more security problems on everyday software.
Node's success has everything to do with the environment itself in combination with the language. The node runtime, the associated stdlib, and most open source/3rd party modules have been written for a non-blocking runtime from day #1. The same stuff can be achieved in plenty of other languages/stacks (e.g. Python + Twisted), but you have much more work to do validating that every single library you use plays nice with async io, sometimes you have more event loop housekeeping responsibilities, etc...
Let's be honest: it is nothing to do with either of those and purely a matter of fashion. In a couple of years at most there will be a new new thing and everything will revert to version 0.1, keeping everyone busy but making no actual progress. Gotta soak up those CPU cycles the hardware people are giving us somehow right? Can't let the users get any of that speed for themselves!
Let's be honest: if you need "fashion" or "idiocy" etc to explain a trend in tech, you don't have an explanation.
Your explanation wouldn't even explain why it was Node+JS that got to be "in fashion" and not something else from the 20000 options.
That's the point. There is no explanation, other than the same reason that bellbottoms are in again this year. Or out, I don't actually know.
We pretend like we're "engineers" or "scientists" but there's nothing objective about what we do...
You mean you can't come up with one. Because for me, which followed the scene for 20+ years, there is a perfect explanation.
I had a homepage in 1994. I've seen them all come and go. This one's no different.
It’s as relevant as saying we don’t write apps in COBOL or Modula2 anymore.
I'm frustrated that better stuff doesn't win in the market as well, but I've been a web developer 20 years and Node's appeal was pretty obvious and exactly as the GP states. Without that it would not have gained traction to become fashionable.
The thing missing in developers that I have decried over and over in this devop/agile movement is that SAs had discipline and an ordered idea and that developers exist to perturb the norm to better effect. The two ideas are not readily reconcilable.
The real innovation that the Node environment and the Javascript language offered is one of marketing to developers who did not know better. Because there were no I/O paradigms in Javascript, one could be created to support this way of doing things, and there was no competing paradigm that people could point to in Javascript to say "Why would I do this when I could just use threads? It's not that hard."
With that out of the way, the floodgates opened, because once the first few people started adopting it because they did not understand threads, it was only a matter of time when "front end" people adopted it, because they did not know any languages other than Javascript. And thus, the current fad was born.