He understood how to put the audience into the point-of-view of the characters in an almost voyeuristic way.
A: He was definitely called "the master of suspense" for a reason, and it wasn't because he made great suspense-thrillers. It's because he understood how to direct the camera to convey suspense with slow shots and tighter close-ups, and his knowledge of editing is what makes his work stand apart from most classic filmmakers. He understood how to put the audience into the point-of-view of the characters in an almost voyeuristic way. We are seeing the action unfold through their eyes, and then he is able to manipulate emotions with camera, lighting, and sound to build up suspense.