Instigation
As summarized for the Museum of Broadcast Communications:
By the late 1960s, ...many viewers, especially young ones, were rejecting shows as irrelevant to modern times. Mayberry's total isolation from contemporary problems was part of its appeal, but more than a decade of media coverage of the civil rights movement had brought about a change in the popular image of the small Southern town. Gomer Pyle, U.S.M.C., was set on a U.S. Marine base between 1964 and 1969, but neither Gomer nor any of his fellow soldiers ever mentioned the war in Vietnam. CBS executives, afraid of losing the lucrative youth demographic, purged their schedule of hit shows that were drawing huge but older-skewing audiences.
The purge was instigated by CBS executive Fred Silverman, following research highlighting the greater attraction to advertisers of the younger urban viewer demographic. Their lack of relevance was referred to in Gil Scott-Heron's 1970 spoken-word piece The Revolution Will Not Be Televised, which alludes to at least seven of the shows that are eventually cancelled as part of the purge, mentioning that as part of the titular revolution, the shows "will no longer be so damned relevant". Another factor in the purge was the loss of a half-hour of prime time programming each night as a result of the Prime Time Access Rule, which took effect in 1971; as a result of the new rule, the networks (all of which had started prime time at 7:30 p.m. Eastern Time before the rule took effect) had to trim the equivalent of seven half-hour programs from their weekly schedules and give them back to the local stations.
The numerous cancellations prompted Pat Buttram ("Mr. Haney" on one of the cancelled shows, Green Acres) to make the observation: "It was the year CBS cancelled everything with a tree—including Lassie".
The first rural-themed show cancelled by Silverman was Petticoat Junction. In September 1970, The Mary Tyler Moore Show premiered on CBS. All in the Family premiered in January 1971 as a midseason replacement. Both series provided the urban demographic, cutting-edge social relevance, and ratings that CBS sought. These ratings successes prompted Silverman and the network to cancel Green Acres, The Beverly Hillbillies, Mayberry R.F.D., Hee Haw, Lassie, and The Jim Nabors Hour at the end of the 1970-71 season. Another series, The Glen Campbell Goodtime Hour, lasted until the end of the 1971-72 season.
ABC also was looking for younger audiences, and in May 1971 cancelled shows that skewed toward rural viewers (such as The Johnny Cash Show) or older viewers (Make Room for Granddaddy and The Lawrence Welk Show). NBC also targeted rural and older oriented programs in its cuts, eliminating long-running programs such as Wild Kingdom, The Andy Williams Show and The Virginian, all of which ran nine seasons or more.
Read more about this topic: Rural Purge