Baseball is more popular than ever in terms of fan support, it’s just that now there is so much more competition in sports to follow. Back then the three most popular sports were baseball and boxing, and college football. The NFL back then, was probably about where the NHL is today in terms of popularity.
Back in the 60s, NFL players had to work real jobs in the off season to make a comfortable living.
My Dad bought insurance from Lou “the toe” Groza, placekicker of the Cleveland Browns.
I agree. Television which started to heavily cover the game in the late 60s - early 70s made the NFL what it is today. It's the perfect television sport and the networks have capitalized on it.
Consider there are many more "football fans" that have never actually been to a football game than those who have gone to games.