Youtube (seems) successful because of illiteracy. Most can't read and video is the only realistic option.
Though this means book characters are all reliably way smarter than average, because they're written by smarties for smarties. Regular folk basically don't show up in novels, except occasional cameos as caricatured villains.
This leads to a puzzle, though. When it comes to fan translations, anime > manga > novel. Why are novel translation reliably awful? There's a few exceptions but it seems at least 80% of translators are simply not fluent in English. A bunch of them are fluent in neither English nor the original Asian.
I suppose it could be full noise. Bigger viewership means higher peak IQ, meaning the best translator is better.