I think the evolution was driven by the desire to have non-technical people be able to maintain websites. The easiest way to do this is a web app, and once you have a web app, making the entire site dynamic is (a) easy (b) opens the door to tons of shiny possibilities.

Obviously, there were significant efforts in the maintainable static site space, such as FrontPage and Dreamweaver, but I think those ultimately lost out to the flashiness of dynamic websites.