I don't think it has evolved. I feel that it became more like a hack, on top of a hack, on top of another hack, and so on.

In the late 90's - early 2000's, HTML started to being pushed into fields that, at my opinion, were unrelated (remember active desktop?). Before you had time to react, HTML was being used to pass data between applications. At the time I was already doing embedded stuff and I remember being astonished to learn that I have to code an HTML parser/server/stack in my small 16-bit micro because some jerk thought it was a good idea to pass an integer using HTML (SOAP, for example).

In the meantime, HTML was being dynamically generated, and then dynamically modified in the browser, and then modified back in the server using the same thing you use to modify it in the browser. It's a snowball that will implode, sooner or later.