Not to mention all that sweet, sweet game developer data and owning one of the most popular social multiplayer games out there today.
FTC is another problem but they would probably allow this acquisition no matter how big it is because Facebook is not in the business of making video games or game engines.
Besides owning Fortnite and major content creation engines for the metaverse like you said another good synergy is boosting Facebook's Twitch and YouTube Gaming competitor Facebook Gaming with Epic's expertise.