Definitely pretty much everyone was anonymous on warez boards and the like. On the other hand, a lot of local BBSs actually had something of a local community in real life as well. And the people accessing Usenet from corporate and academic accounts often used their name and affiliation.
In the mid-2000s I was at school, where we were simultaneously being taught (in 'Information and Communication Technology' lessons) never to use a real name online [0], and signing up to Bebo & MySpace with our real names.
It's (there beginning to exist people) growing up with the internet that all but killed that, I'm sure of it.
[0] with some limited web ring/social network type site for schools, for which we given aliases and then, I don't know, wrote BBcode and marquees and stuff about our school-safe interests and hobbies
Into the early 2000s, everyone still knew never to use a real name online. Murderers would probably get you or something. Don't want randos knowing you you are. Besides, handles were cooler. Some well known people had publicly known aliases, but aliases were the norm... like on HN.
In my bubble, it was FB that really broke through this. I heard about fb as a social network, but with real names. That way you could friend people from real life. It was actually quite a revelation, like a public address book... very useful.
Anyway... Zuck is, IMO, more of an "eye for the tides" guy than the tide itself. He realised that "relentlessly cataloging and indexing information about every single person on the planet in a way that anyone can search instantaneously" was happening and he decided to be there first.