I feel like as a gamer the older internet communities were heavily influenced by abrasive and antisocial gamers and message boards like 4chan and something awful were sort of like a bottom layer of internet forums. The big message boards where like a level 0 of internet memes and culture that would then float up to the more mainstream layers of the internet.

The late 90s and 00s were also just an edgy time for "edgy" humor and edgy behavior and boundary pushing behavior and while some had a talent for towing the line while still being funny or thoughtful, we're talking a younger internet driven by mostly teens, tweens, and socially awkward young adults so we get the standard newgrounds flash video.

There were also small close knit communities of friends from around the world and happy parts of the internet, and more wholesome spaces, but the poison was already floating around the water in the well even before algorithms and bots were introduced to further enhance the churn and toxic behavior.

I think a good example of this is message board discussion on gamefaqs in the 00s. A few steps above 4chan in terms of attitude the Next Gen Gaming board was mostly just trolls trolling trolls and people arguing in bad faith. The general style of argument would be to quote and reply like every sentence in your post instead of just having like a good faith discussion.