We were all nerds, mostly descended from Europeans, associated with post-war higher education, learning through math or reading, and critical thinking. We had (inside the US) geographic diversity, but otherwise had very similar social norms. The wide range of social norms from UC Berkley to WUSTL to MIT.
Everybody you met on a BBS was likely to be interesting to you, because they were another person with interests significantly like yours.
The worst parts of the "open" internet today are full of people who see your interests as antithetical to their own interests.