I don't doubt the supply side of the market, it's the demand side that puzzles me. If people wanted to pay me thousands of dollars to talk about ND football on a webcam, I'd do it in a heartbeat. I just don't know why anyone would want to (yeah, I know nobody does, but you get my point).
People watch what's entertaining. Even if it's not your cup of tea I don't think you're giving the people who make a living doing this sort of thing enough credit. There are millions of people who try every day to start a money-making channel and fail. The one's who do usually have something to say or hit a chord with an audience.
I'm not a fan of Pewdepie (sp?) but I know I'm not his target audience. His audience is middle school boys who laugh at Adam Sandler movies and watch First Take. (I don't say that in a bad way, that's a valid audience and I probably would think he was hilarious if I was in 6th grade.)
I am a huge gamer though, so channels like:
Extra Credits
<iframe width="560" height="315" src="https://www.youtube.com/embed/ERR1F-zoTVg" frameborder="0" allowfullscreen></iframe>
Matthew Mitosis:
<iframe width="560" height="315" src="https://www.youtube.com/embed/UScsme8didI" frameborder="0" allowfullscreen></iframe>
and SuperBunnyHop
<iframe width="560" height="315" src="https://www.youtube.com/embed/iMK-kajdgMA" frameborder="0" allowfullscreen></iframe>
are all great for me and I watch them extremely regularly. For movie reviews the RedLetterMedia guys are my go to, and for tech reviews I look to Marques Brownlee. Do you like interesting facts about linguistics? Check out Tom Scott. And that's just scratching the surface of my Youtube subscriptions.
All in all, Youtube is like any other form of extremely popular entertainment. It can be as dumb or as smart as you want it to be.