Star Trek into Darkness Co-writer Roberto Orci explained why a certain villain was included in the film.
According to Orci, the villain was a result of wanting to relate to Star Trek history. Spoilers behind the cut for those who haven’t yet seen the film.
“[Damon Lindelof] argued for Khan from the beginning and I argued against it,” said Orci. “The compromise that we came to was, let us devise a story that is not reliant on any history of Star Trek. So, what’s the story? Well, we have a story where our crew is who they are and they’re coming together as a family. Then, suddenly, this villain arrives and his motivations are based on what happens in the movie. They’re not based on history. They’re not based on Star Trek. They’re not based on anything that came before. They’re based on his used by a corrupted system of power that held the things he held dear against him and tried to manipulate him. That story stands alone with or without Star Trek history. That’s how we approached it, and God bless Damon for going down that road.”
However, Lindelof was persistent when it came to wanting Khan. “So, once we had that, that’s when Damon came back and reared his ugly head and said, ‘OK, now that we have that, is there any reason why we cannot bring Star Trek history into this?’ And he was right,” said Orci. “So we ended up sort of reverse engineering it. We started with, ‘What’s a good movie? What’s a good villain? What’s a good motivation? We cannot rely on what’s happened before. Now that we have that, can we tailor this villain into something that relates to Star Trek history?’ And that’s what we did. So, step one was ‘Don’t rely on Star Trek.’ Then, step two was ‘Rely on Star Trek.'”