People (Ad people) simply noticed that the ads were a communication channel in and of themselves, and using the (for example) facebook tools to lazily target a particular demographic, they got huge numbers of eyeballs. Stir in some classic astroturfing and social-media influencers (Derisively known as shills), likes, comments and you've got a quick minilove and truth. Except even better because anyone with cash who resides in any country on earth can buy in.
The author was pointing out the now obvious fact that "tech companies" look like an information service for connecting friends but are actually ad generating theme parks. Since the value of the data your users bring is only very useful if you have a lot of it, the organizations who have replaced both Nielsen and News Papers have simply followed the incentives and coalesced into larger and larger gravitational bodies. By having all the content, users, tracking pixels, sales data, and ads, it increases the value of all of those things if you can meaningfuly connect them together by engaging with users through next-generation enterprise-grade disruptive orthogonal innovation at-scale.
They're saying a centralized web is more valuable to its corporate sponsors, because when there are fewer places you need to advertise or track/monetize user data in this world, the corporate value compounds even more. Likewise abusing these themeparks will be even more effective, because whatever mechanism sells soda pop will likely also sell antidepresants and anything else.
Walking into the stables might get you a big sack of oats, but you wont find anything other than what they hand over the gate.