[Jtsummers]

It's cyclic. When I first joined over a decade ago there seemed to be a lot of technical posts and discussion at the time, which gave way to a lot of SEO discussions, which gave way to technical discussions, then shit tons of Erlang (not that I minded), then other stuff for founders, etc. People tend to post interesting things which leads to other interesting and related things. So you'll see a lot of a certain topic or field, maybe a surge in new users or user activity because it interests them, and then some new topic or field becomes dominant for a while and appeals to a different subset of users who become a bit more active with submitting, posting, and voting.