I'd make a guess that the video in question hijacks the reward system in the brains by showing repetitive, almost identical, but slightly different events: kids

I'd make a guess that the video in question hijacks the reward system in the brains by showing repetitive, almost identical, but slightly different events: kids still learn to predict the world and when they see their prediction as correct, their brains produces dopamine. It doesn't work on adults because for an adult brain there's nothing to predict there.