I wonder what happened? I have been blown away by some of the older explainer videos from the 40s and 50s, esp. some of the military training videos for vehicle repair, electrical engineering, etc. Very concise and very clear explanations, always with visual examples. Today, we have things like 3brown1blue that are kind of like that, but in general you don't see information transfer like this either online or in school (at least not in my experience).