Facebook is a virality engine. How do you get content that's appealing to the widest variety of people shoved into their faces?
The popularity of a President almost always goes up by starting a war, because the American public loves war. It's how Bush Jr. got the popular vote after losing it so miserably the first time.
People love hate, so an engine aiming to do nothing but push content with the possibility of going viral, viral, will endlessly promote the most inflammatory content. It drives engagement! The speech doesn't matter at all; it could be anything. On their other popular platform, a platform with a younger population, the most popular post is literally a picture of an egg. It's more a video game than a "marketplace of ideas."
Of course, the obvious solution would just be for Facebook to stop suggesting this content algorithmically rather than removing it outright, but hey, I'm not Facebook. It's not an attack on speech for a company that makes money off of suggesting content to other people to stop suggesting some variant of content, though, because again: the content never mattered.