This is not really true in my experience. The vast majority of instructional videos and video essays are just repackaging a text resource, often just the list of references from Wikipedia. I think you’re just falling for the veneer of professionalism that makes YouTubers popular, but remember it doesn’t actually mean they know what they’re talking about any more than a random forum poster. There are of course exceptions, but the glut of instructional videos is just because they’re profitable, not because they’re actually full of unique knowledge.