The reason this pattern is so common is that most people take their cues for what to care about from the media, and the media take their cues from a presumably small and difficult-to-identify group of thought leaders (some combination of editors, PR firms and people with extremely respectable positions).

It is basically a self organising system around a very small pool of original thoughts. It is pretty remarkable how stuff can completely slip the general discourse because it never catches on in the in-group.