[LostTrackHowM]

If my memory is correct, I discovered PG's essays from Slashdot, and through them reddit, and through reddit hn.

And this reminds me of how some people theorize that life on Earth came from another planet.

In one way it answers the question, but also does not answer it at all.

My guess for origination online communities from scratch would be advertising and already having a small community. Well obviously content too. But I think the reddit founders early on pretended to be many more people on reddit, because no one wants to join an empty community.

The founders provided the startup community. PG's essay were the advertising. And both slashdot and the people who posted PG's essay there, where the advertising of PG's essays.