I don't have references because of the intentionally opaque way this stuff is negotiated; but the level of consolidation was one of the most eye-opening things

I don't have references because of the intentionally opaque way this stuff is negotiated; but the level of consolidation was one of the most eye-opening things I found when building a video product in the space back in 2016. Rooster Teeth (owned by Otter Media, which is WarnerMedia/AT&T) is a good example here; they have their fingers in a lot more YouTube pies than is obvious at a glance. But yeah -- the real money in video is still in negotiated campaigns that target a specific channel or set of channels. There are only so many ad buyers, so there are benefits to centralizing ad slot sales as well as SSP activity. Those kids doing a billion views have a magic combination of personal charisma, work ethic and well-connected, pushy parents in the media industry. Things were different pre-2015 but the level of sophistication required to get big in online video is much higher than people think. There are a lot of talented, charismatic people out there making videos; the ones who find financial success are the ones who can amplify their voice above the crowd (which really just takes money).