It was, though? And continues to be. In the mid-90s, you could pretty easily find illegal material without looking too hard. It was already illegal by the Child Protection and Obscenity Enforcement Act, an early Internet bill which mostly said "illegal porn is still illegal, even if it's on a computer", and it also required producers of pornography to keep detailed records on talent & crew in the production. By the mid 2000s, large sweeps of enforcement happened, and thousands of studios without proper documentation and recordskeeping shutting down. The CIPA act required schools, libraries and public places where children could be to install internet filters, and make policies preventing children from viewing such material.
Pornography isn't illegal in the US, it's pretty well-regulated, and once the Internet started entering mainstream culture, it quickly adapted to the existing legal framework and culture that was already there.
This is, of course, a very US-centric view, but so is a lot of early Internet history, along with its culture.