Sure, there's a long tail of people who do free labor for YouTube by publishing niche reviews or science lectures and never seeing a penny, but if they disappeared overnight, I don't think that YT viewership or revenue would budge.
YT might have gained steam as a video equivalent of the old Reddit, but it converged on mass-consumption of professionally-produced, focus-group-tested content.
By any precedent YouTube is radically decentralized. Yes, the view concentration follows a power law, and the power law beats the long tail, but you have to add up thousands of channels to get a majority of YouTube views. Think about how that compares to the overall media landscape. Any two TV channels would yield a majority of viewers. The diversity and decentralization on YouTube is much greater.
I think a big factor is that it's low friction. Just open the link or search whatever you want and it plays. It's not like cable where you need to sign up for a service, or Netflix where you need to scroll around in previews selecting for your next show, it's always on your phone, laptop or TV fast and free.
It's successful because it's mindless, people can just pull something up and consume content. If they start pushing more unskippable ads, or requiring subscriptions or accounts to view, their viewership would go way down and people would move on to next easier thing.
And that's not even getting into the content part, where the stuff you want is probably on like 15 different services and you're either gonna pay through the nose for something you barely need or you'll have to miss a whole bunch of things because it's less of a hassle that way.
Yeah, it's a lot easier when almost everything can be found on a couple of sites for free, where you don't need an account to view most videos and where everything is about as predictable as it can be.