Have you ever wondered. . . how religious movements get started? Usually, we think of them as a product of highly charismatic evangelists. . . but the spread of any new and contagious ideology also has a lot to do with the skillful use of group power.
Horror movies started to wane around the onset of World War II, and after World War II, when all the troops came home, people weren't really interested in seeing horror movies, because they had the real horror right on their front doorsteps.