back in the 60s and 70s their programing was centered on rural America. It got them good rating, very good ratings but there was a problem. Their viewers were not the buying public. ABC and NBC were able to pull in just as much ad dollars as CBS although overall viewship was lower for the two. People who purchased stuff watched shows on ABC and NBC.
So while CBS was running Beverly Hillbillies, Green Acres, He Haw, Petticoat Junction, Gunsmoke, Ed Sullivan show
NBC was running Star Trek, anthology show Name of the Game, Get Smart, I dream of Jeanie, Laughin, Man from Uncle
and
ABC was running Time Tunnel, Voyage to the bottom of the sea, Bewitched, The Invaders, Shindig, Batman
CBS didnt really get with it until Norman Lear brought out his show that went to CBS.