That's game-plan/coaching, basically Steve Kerr finally figured out how to deal with the Thunder's plays, and setups, and managed to disrupt them.
When you look at the film, check to see how they position, the 1st 3Q's the Warriors stand between the basket, and the player, about 2 steps away. in the 4th, the Warriors stand diagonally(slightly in front of the player, waiting to intercept the pass, rather than defend the basket), and that press worked, it upset the rhythm of the Thunder.
Also on offense, the Warriors played more compact, with a wide outlet(it means that 4 players step-in towards each other, and the wing-player stays deep in the corner. It created that extra-room making it impossible for the help-D to switch over.