I can guess at the difference. Peloton is sort of a rapid example: Covid hits, they all of a sudden have a market for people who can't go to the gym. Their stock shoots up, they hire a bunch of people and they are advertising left and right. Fast forward to restrictions being lifted and suddenly their market is pretty much gone overnight. They had a big layoff a few months ago and are now trying to get bought by any big corporation like Meta.
It isn't exactly that way for Meta-faceplant, but it is along those lines over a longer period. Almost overnight, the ability of users to opt out of their data being sold and their literal cash cow is now hamburger. That's part of it. People enjoy a thing like that for what it is for a while and then move on to something else when the shiny wears off, and the shiny has definitely worn off. They staved off irrelevance by buying some other newer mainstream apps, but in the end, they aren't really offering anything new that people want as far as I can tell.