I don't think Fortnite is a good example of Epic "knowing what they're doing". The game was stuck in development hell for many years during the closed betas and

I don't think Fortnite is a good example of Epic "knowing what they're doing". The game was stuck in development hell for many years during the closed betas and they really didn't seem to know how to fix the game (it took them 6 years to release the primary game mode as "early access", which it is still labelled as). It never really took off until a small part of the team spent less than 2 months on replicating PUBG's battle royale mode into the game as an experiment. That's not really "knowing what to do", that's more some kind of luck or serendipity.