Trump has long since made a habit out of doing that. All the times he has promised to fix something in two weeks (it is always two weeks), ISIS, healthcare, the Middle East in general, Ukraine war, etc. etc. Two weeks passes, and it is as if he never promised anything.
I listened to Larry David explaining the origin of this joke while on Conan’s podcast. Apparently, when Larry worked at Saturday Night Live, he was struggling to get a skit onto the show and lost his cool. He went and yelled at the boss, telling him he was quitting. Afterwards, he realized that he needed the money, so he came back the next day like nothing happened.
Similar to the chocolate eclair out of the garbage can. Jason Alexander apparently was confused by the bit, got upset and started yelling “who would even do such a thing?!” To which David said “I would! This scene is literally something I did!” And from that moment on, Alexander just treated George Costanza as being Larry David.
Honestly thought Larry David inflated his own value to Seinfeld after the show ended.
But after binging on all of Curb Your Enthusiasm… Yeah Larry is quite a guy and the soul of Seinfeld.