I don't think Facebook is "evil" by design, but the end result is the same. The framework is as follows:
There were probably thousands of internet companies that competed to be the dominant sites in the 90s and 00s. By several orders of magnitude the predominant business model is ads for eyeballs, and the predominant network effect scales with number of users.
Several factors influenced success but, on average, sites that captured user attention more effectively got more views and a larger userbase. Thus there was overall selective pressure for addictive properties, and sites like Reddit, Twitter, Facebook, Instagram won over sites that were less able to hold attention like Blogger, Digg, MySpace, etc.
We cannot know, for example, that Jack Dorsey was knowingly trying to maximize outrage with his character limit, which feeds into the "two-minutes-hate" emotional addiction. But we can be sure that he was trying to maximize several KPIs like # users, bounce rate, time on page, etc.
The result? The dominant sites today == the sites that are best able to capture attention!
How successful were they? Not only have they captured a huge portion of time people spend on the internet, the amount of time people are on the internet has itself increased! So they won over other websites and also grabbed attention away from traditional media, newspapers, random thoughts while standing in line, uninterrupted dinner, etc. time.
What's the problem? I think the major challenge is that these sites feel more effective at shaping attention than many drugs (no reference for this yet)!
This parallels the opioid crisis -- maximizing certain good pain relief characteristics (short onset, hits opioid receptors) just happens to be addictive. I doubt the Sacklers cackled during dinner and clinked glasses at the future misery they were causing, but it's pretty damn easy to convince yourself that you're doing the right thing when the money is rolling in.
Jack Dorsey similarly thinks he's saving the world but he's probably the single most responsible person for the "populist politician" phenomenon.