I don't know exactly when, but I think it had a lot to do with the fact that in 2004, Python, Ruby, and yes JavaScript were all fairly niche. (This might be ha

I don't know exactly when, but I think it had a lot to do with the fact that in 2004, Python, Ruby, and yes JavaScript were all fairly niche. (This might be hard to believe for some, but it's true. GMail had just come out, and it was one of the first web APPS in JavaScript, certainly the first really good one. Paul Graham wrote "the Python paradox" https://paulgraham.com/pypar.html https://paulgraham.com/pypar.html , and Ruby on Rails didn't exist yet.) JSON maps well to core data structures of Python, Ruby, and (obviously) JavaScript, but XML doesn't. XML seemed to be associated with Java. There was a lot more ceremony around the APIs. You didn't just manipulate data; you had to create classes and call methods. So basically neither JSON nor XML are really convenient in Java. But JSON is very convenient in the dynamic languages. You don't need extra abstractions / layers / code generators -- it's just "there".