It wasn't invented in the 1990s, but a strength of HTML was its relative simplicity. From my recollection, early attempts at hypertext added complexities like bidirectional links, which required more complex software to serve and develop documents. It may have been an amazing tool, but it was also one which a world accustomed to references (which is pretty much a unidirectional hyperlink) was not prepared for. It is also a facility that the modern web has proven largely unnecessary. (It has few uses outside of research.)