Warning: SPOILERS ahead for The Last of Us season finale.
Although Neil Druckmann and Craig Mazin have changed a few things here and there, the ending of The Last Of Us has never been up for debate. While it‘s a bit tragic and calls Joel’s morality into question, the ending is absolutely integral to the themes of the story being told. Strangely enough, original Last of Us game creator Neil Druckmann was open to changing the story’s ending if it fits the needs of the show, but fellow TV Last of Us co-creator Craig Mazin didn’t even give it a second thought.
During a Last Of Us press conference, both of them spoke about the process of writing. Any deviations were pretty minor. As Mazin put it…
Neil was, I will say never, I honestly mean this, I don’t think he was ever the guy who said, ‘No, we have to do it the way it was in the game.’ I was that guy, because I’m a fan. And Neil, in the smartest, most generous and flexible way, was always open to the process of adaptation. He understood what adaptation meant … But, the ending, there was never a question. As a player, I got to the end, why would I ever want to change that? It’s awesome.
Hence, as in the game, Joel chooses to save Ellie at the cost of a potentially world-changing cure for the Cordyceps fungus. Since Ellie is naturally immune, the Fireflies were planning to extract this cure from Ellie. Unfortunately, the process would kill her. Joel just spent the whole course of the series learning to love Ellie as a daughter, and since he has nothing left without her, losing her would just be too much for him to bear.
You can watch the full season of The Last of Us on HBO Max.