Honestly, while fun, those videos don’t provide too much value per GB - and I say that as someone who’s watched almost all of them. Their main actual benefit besides entertainment is (IMHO) getting people interested in the relevant field so they study more thoroughly. They often explain simple yet dazzling concepts which get you hooked but don’t provide much value on their own, and don’t directly enable you to solve real-life problems. Even more involved videos like those by 3blue1brown are still edutainment at their core, as acknowledged by the author. In an apocalypse (which, let’s face it, is the most likely reason the internet would indefinitely go down in a developed country) you would be much better off with engineering (mechanical, electrical, etc) literature and textbooks, maybe a couple science textbooks for good measure (I have a drawer full of the Feynman lectures in case something like this happens).