Well, it became mainstream by the late 1990s (IIRC the pets.com superbowl ad was 1999). But in 1992 or so it was still a bunch of Gopher sites (this new fangled "World Wide Web" will never displace this technology...) and MUDs being used by college students and hobbyists.
In 1993, UNC Charlotte had one computer in its library with a big sign next to it explaining what the World Wide Web was. It would be a few years yet before home computers became commonplace in that region, and late ‘90’s before everyone was more likely than not to have a computer at home, and to have some sort of dial-up internet. I was purchasing domains in 1997-1998 for $3/ea, I believe (I wish I could have known then what I know now…). I sold my first website design job in ‘96, which would probably coincide with when many businesses around Charlotte were establishing websites for the first time.
Fun to think about.
In this context, “mainstream” may just be another way to describe Web 2.0.
The problem with the internet today is it’s a bunch of disconnected privately owned silos.