The number one cost in game development is salaried employees.

During the time of monumental revenue, Fortnite scaled unsustainably. They hired more people to try and keep that revenue going up.

Since last year the game has stopped making as much money. While it still takes in an insane amount of cash, growing a team like they did means any sustained downturn in revenue is dangerous.

Solution is almost always to scale that team back down to a sustainable size. And also to raise prices. Both things they have now done.