Actually it goes deeper than that. FakeBook promotes the divisive stuff to keep their users "engaged", i.e., forwarding and sharing it which results in more ad revenue for themselves. You see they don't mind helping in a big way dividing the country in their quest for the almighty dollar.
https://www.seattletimes.com/opinion/the-game-is-rigged-a-former-marketer-shows-you-how-big-techs-advertising-practices-harm-us-all/