His videos revolve around the stunts / pranks / jokes / misadventures of his "friend group" ("the vlog squad"—consisting mostly of former viners like him).
Each video gets ~10m views
All his friends have YouTube channels, but none even attempt to match his level of quality. They're meandering 15 minute self-portraits that feel like the cutting room floor of David's vlogs.
I think the answer is probably weirder:
They don't want to their videos to be too interesting because maybe they don't want David to think they're competing?
(He's given away like a dozen cars, and generally spends lots of money on things for videos.)
It's kinda Amazon-esque