Few other shows could reach the height of popularity that The Vampire Diaries did in its heyday, and unsurprisingly, it continues to dominate fans' imaginations even today. However, like every great fantasy show, TVD jumped the shark -- sometimes. The phrase originated from a scene in Happy Days where Fonzie literally jumped over a confined shark, which stretched the imagination just a bit too far for the audience to suspend their disbelief.
Source：https://www.cbr.com/times-vampire-diaries-jumped-the-shark/
