What are the reasons horror movies returned to the mainstream in the 1970s?

Answer 1

Horror thrives in uncertain times, channeling “real world” fears into metaphoric monsters. The late 1960s and early 1970s saw a wide range of “real world” horrors, including political assassinations, race riots, cities on fire, self-immolating monks, and the ever-present televisual spectacle of the war in Vietnam. Add to that the changing mores of the counterculture and the growing specter of political corruption and there was plenty for America to be nervous about. Critic Robin Wood sees this era’s horror films split into two camps. Some were made independently by young leftist filmmakers like George A. Romero, Wes Craven, and Tobe Hooper (Night of the Living Dead, The Last House of the Left [1972], The Texas Chain Saw Massacre [1974]) and presented an apocalyptic vision of America destroying itself from within. More mainstream horror films from the Hollywood studios (The Exorcist [1973], The Omen [1976]) still tended to uphold the need for white patriarchal capitalism to defat the monster.