The Uncensored Free Speech Original™ can remain decent for surprisingly long—or at least it could in the old days. Community norms can shout down or ignore the bad actors, so long as they remain uncoordinated. However, uncensored alternates are magnets for those who shit up the moderated original.
One thing to remember is that the old days had much narrower demographics: computers cost a lot more as a function of income, and connectivity was even more expensive in the dialup era so it skewed well-educated, professional, etc. You had cranks, of course, but they were less likely to find a critical mass audience and nobody was trying to use them to reach a large audience.
Also, community norms massively included censorship. BBSes booted people who annoyed the sysops, Usenet had moderation even if it wasn’t very secure and some servers aggressively filtered the feeds they carried for reasons in addition to space consumption.
