Was a lot of it classic word of mouth, email, etc.?
I imagine something like that, but I’m wondering as I feel like there may be some useful pieces of knowledge that may be worth recalling as people gradually start to move back out of the more centralized sites/services.
IIRC, that was powered by Mozilla Directory (AKA dmoz!). RIP. I was an editor for a couple categories for a while. Curated link lists looked like they might be the way to go, but search engines ended up getting really good at the time so the project kind of declined.