The very first sentence of the article disproves your claims.
It has nothing to do with caffeine, blue screens, or artificial lights.
It's the first sentence!!
"On dry nights, the San hunter-gatherers of Namibia often sleep under the stars. They have no electric lights or new Netflix releases keeping them awake. Yet when they rise in the morning, they haven’t gotten any more hours of sleep than a typical Western city-dweller who stayed up doom-scrolling on their smartphone."