I agree with claims that Postman predicted Trump's rise back in 1985:
The book is written about television, but the main ideas are still applicable to online newsfeeds and social media.
The book unpacks the phrase: "the ideas that are convenient to express become the content of a culture". If the most convenient form of communication is long-form writing in newspapers or pamphlets, people will get their information from (long-form writing in) newspapers or pamphlets. If it's television, they will get information from (visual, snappy, "entertaining") video. If it's Twitter, people will end up talking about ideas that can be conveniently expressed in 140 characters or less.