You see this puzzle is mastery at it's best: You sacrifice a pawn, a knight and a rook in exchange of a bishop but you gain the best position ever: You take down your opponent's only crownable pawn, you clean the board so there's no long range piece that could take down your only crownable pawn and, at the same time you leave his king far enough for you to crown easily and take down his king, this is mate at a great level.