The show debuted twenty years after the fictional Arnold family's sitcom-esque life events took place. Place - this is presumably California, and that California became Wondrous enough in 1968 to our culture to warrant a nicely done television show.
(pretty kickass run-on sentence, yes? ha ha!)
A debut after the nation just collectively drank its way through the Super Bowl? I bet that cost a fortune to put together, but the producers had to catch us at just the right time when our guard was down as a nation. This is the TV climate that wore America down the previous year. Small wonder that Roseanne, (the anti-Wonder Years Mom) was a flying success, too!
Americans are weird. Can I get a witness?