Imagine there was a free or quasi-free API for Facebook. Facebook would lose large amounts of money on content because they can no longer monetize it with ads.
Facebook pays their moderators though. If reddit would pay subreddit moderators, top commenters, users that submit very interesting stuff, and in the case of Apollo, people creating the Apps that enable you to use Reddit in a pleasant way, then the story would be different.
Facebook moderation is especially awful, however. Pre-2022 (at least) a fairly common tactic against anti-Kremlin posts was to have the troll farm report the user and/or random posts of theirs in large amounts. Done! Many fought it out and got reinstated after several weeks, but some just gave up and quit Facebook in disgust.
(And that without mentioning the “Khokhlov” incident: “khokhol”, genitive plural “khokhlov”, is in addition to its literal meaning of “tuft” a fairly standard pejorative for Ukrainians; unfortunately for Facebook, it’s also the surname of physicist Aleksej Removich Khokhlov, presidential nominee and later vice-president of the Russian Academy of Sciences, which some years ago got several science-adjacent people and IIRC even a science monthly covering the election suspended for “hate speech”.)