What form it takes isn't as important as the fact that it supplies enough content / entertainment / methods of consumption that one can subscribe to it and have 100% of their bandwidth filled, to the exclusion of competing narratives.

Talk radio was an imperfect expression of this, because radio isn't portable in the same way that app-based social media + mobile devices / Fox News are.

But it's entirely possible to prevent someone from ever being exposed to a contrary narrative, simply by filling all their available time.

That's the central premise of Elizabeth Eisenstein's The Printing Press as an Agent of Change (1980) https://www.cambridge.org/core/books/printing-press-as-an-ag...

I've compiled a related bibliography that gets at other aspects, including social and online media.

https://old.reddit.com/r/dredmorbius/comments/7k7l4m/media_a...