Or - this thought scares me the most - FB actually doesn't care about facts?
I challenge you to find a point in human history where "journalists" weren't putting their fingers on the scale. Look at the journalistic antics of someone like Benjamin Franklin for instance.
[1] https://thefederalist.com/2021/12/13/facebook-quietly-admits...
This means most newsrooms can't afford as many editors and fact-checkers, can't dedicate journalists to complex subject areas, can't afford to have journalists spending weeks or months on particularly complicated and deep stories, etc.
They surely knew what the consequences would be of starving newsrooms of income, yet went ahead anyway and didn't bother to even think of let alone implement alternative models to preserve valuable news.
It's a rather typical SV hubris, isn't it?