That “somehow” is pretty obvious: they had already built all the assets for a great multiplayer FPS-esque, and already had a whole marketing department spun up to get people to play it. Once they decided to pivot to Battle Royale as a game mechanic, they spent a month on rewriting game logic, and then had a nearly-finished AAA Battle Royale game on their hands with a staff ready to sell it, with more polish than existing entries in the genre and no other studios close to catching up to chase the fad in time.
Business take-away: if you build for a well-established, very competitive market, and then—near the finish line—pivot into a new and (as yet) less-competitive market where you can still reuse everything you built, the extra polish you had to put into your product to get it to stand out in the heavily-competitive field, will make you stand head-and-shoulders above everyone else in the less-competitive field.
(I’m trying to think of other good examples of this effect in the business domain but coming up short. Anyone?)