It's certainly possible to come up with explanations -- Moldbug commented on OB; the DE seems fringe due to memetic immune disorders to statements generally accepted as true around LW; LW primes you to suspect social consensus; etc. -- but are explanations necessary?

Not many LWers identified as NRx on the survey, and not many NRx writers post on LW. I would not be surprised if the overlap between LW and, say, conlangers turned out to be about as large as the overlap between LW and NRx.

There is also a non-negligible overlap between NRx and conlangers, which is why I used that example, and also why I don't think there's anything more going on here than "there are only so many Americans who will join groups of people who do complicated things involving words on the internet".