Good article, but scary.

One possible explanation is that for any given thing being investigated, there's some chance of an effect size initially larger than it should be, and some chance of it initially being smaller that it should be. If by chance the effect size starts out being too small, the investigation of the thing never takes off. If by chance the effect size starts out too large, a ton more studies are done and regression to the mean happens.

Alternately, it's possible that lots of initial studies have flawed methodology. Then, as more studies are done on a topic, the methodology becomes slowly more refined and the effect slowly goes away.