White is considering Rxh5. Would Black be able to recapture with his queen, or would he be scared off by the thought that White then has QxQ? The point to notice about QxQ for White is that it removes his queen from his first rank, where his king is stuck; and meanwhile Black has a rook on an open file that can drop to the back rank with Rc1. Look for White’s reply to that move and you see Rf1, interposing his rook; but then notice as well Black’s bishop on a6, which then permits Black to play RxR#. So the initial idea Rxh5 is made unsafe for White by the bishop all the way over on a6—a study in how pieces that seem disconnected may have tightly interrelated interests.
The possibility of a back rank mate easily can create connecting possibilities of these sorts, because its workings can be dramatically affected by the comings and goings of pieces from different points along the rank and in different directions. A more specific lesson of the case is that a bishop aimed next to the enemy king should not be underestimated. It may not be able to attack anything there by itself, but it can provide cover for a heavy piece on the square that may arrive in any of several ways.