This position illustrates why skewers take practice to see. If you look casually for pieces lined up with Black’s king, it would be easy to conclude that there is nothing except perhaps the queen on d7; and that would be correct if we only were concerned with pins. But since we also are looking for skewers, the rook that lies behind the king on f8 is another target to notice. Realistically you might be as likely to find the idea here by looking for any checks you can give and seeing Bh6+. Since the bishop has backup from its queen it can't be captured, and again interposition is impossible. The king must move. When you can give a check that forces the king to move, taking whatever lies behind it is something to consider automatically. White’s next move is BxR.