While Simon’s return to his pre-crown state was a happy event, it also undid the development that Ice King had undergone throughout the series. After getting empathy from Finn and Jake and reuniting with Marcy, Ice King had come to feel happier, stopped kidnapping princesses, and actually became like original Simon in many ways. His statement at the end of Elements about being a unique individual made this development feel very meaningful, and the lesson from that incident was that it was best for Betty to stop trying to “cure” Simon.

Yet this is what makes the ending so ironic and sad. Simon may have come back, but he was then forced into a situation where he can’t be with the person that would make his life feel completely fulfilled. When you think about it, both Ice King and Betty would have remained alive and would have been fairly happy if Betty had stopped trying to “save” Simon. But instead we got a very mixed conclusion where one of them will seemingly always feel at loss because they can’t be with the other.

The most tragic part is that Betty had gone on her Golb mission while probably knowing the risks of it, yet she couldn’t keep from taking those risks because she wanted to be back with Simon so much. She didn’t get what she wanted, but at least she tried her hardest.