This was enlightening. My reasoning for choosing to dive into my chosen topic of the factors that make a movie great and successful is to find gems like this to help me in my own filmmaking journey. This reminds me of a Bonnie and Clyde type of movie. Regardless of the ending, I (and the audience) put value on them making it out together or dying together as a couple. It really wasn't about what situation they ended up in, it just mattered that they made it out together.
Doran is confirming that in her research. It's about the relationships among the characters more than the ending. Another example would be the Notebook. I was told I needed to watch that movie because it was a classic. In all honesty, it was terrible that they both died at the end. Not a happy ending at all. However, it's considered such a great movie because of the undying love and bond that the two shared.