ERM, FB itself admited they made a research regarding emotional response to the content they show.

FB/X modus operandi is keep as much people for as long possible glued to the screen. The most triggering content will awaken all those "keyboard wariors" to fight.

So instead of seeing your friends and people you follow on there you would mostly see something that would affect you one way or another (hence proliferation of more and more extreme stuff).

Google is going downhill but for different reasons - they also care only about investors bottomline but being the biggest ad-provider they don't care all that much if people spend time on google.com page or not.