What's the significance of "Jump the Shark" from the Happy Days episode?
From my understanding, these fairly often-used phrases, "Jump the shark," or "Jumped the shark," are attributed to a certain episode of the sitcom Happy Days. I may have seen only about a dozen or so episodes of that series, years ago. I don't recall watching the entirety of the shark episode. My questions are, how popular was Happy Days at the time of the shark episode, and why did the act of Fonzi jumping over the shark on water skis come to symbolize the decline of something (TV show, movie, game, book, and anything else)? Was it the apparent ridiculousness of Fonzi wearing a leather jacket while doing the jump, all the while there was the looming threat of a shark involved? Is this connected in any way with the popularity of the Steven Spielberg film Jaws, and what it brought to the fame/notoriety of sharks in popular culture? I think I'm most fixated on why "jumping the shark" is always meant to mean that something has faded in popularity. I would be interested in reading the story behind the phrase's connotations, especially in connection to the show Happy Days.
"A New Kind of Man" (John Foxx, 1980):
https://www.youtube.com/watch?v=tt4oi-PRbN4