It's because when Sesame Street took off, it became MUCH more popular than the Ed Sullivan bits. Yeah, the shows Ed Sullivan and the Today show were popular, but Sesame Street was something brand new with it's own flavor, characters, etc. When Sesame hit the airwaves, it became so popular that when 1974 came along, the early Ed Sullivan bits, commercials Sam and Friends, etc. were overshadowed by the popularity of SS.