First, they try to cause addictive behavior. And second, they intentionally create rabbit hole echo chambers that can be manipulated and leads to radical behaviors.

And the experts they interviewed knew what they were talking about because they were the ones that were involved with the programming.

EDIT: They weren't trying to be sinister. They just wanted to keep users around longer so could make more on them with Ads. But it got away from them. And now the thirst for $$$ and quarterly reports is stopping them from making the needed changes.