Before posting the question, I did a Google search and found some sites that attempted to address the question. None of the answers were completely satisfying. (At least, they raised follow-up questions in my mind and were not perfectly consistent with the movies. One of the comments on scifi.SE pointed this out, noting that the answer was inconsistent with the movie itself. No one replied to this comment, and I assumed the site was not focused on the movies so much as the entire body of canonical work.) So I came to this site looking for a movie-specific answer. I did a search and read through ~5 questions that other people had asked here. No one had asked this particular question on Movies.SE, so I asked it here.
Another user posted this comment:
Assuming the question is non-trivial, does the fact that it has been asked elsewhere on the Internet prohibit someone from asking the same question on Movies.SE? Even if we assume that the question has been answered adequately on other sites, would this mean it shouldn't be asked on Movies.SE? Movies.SE requires users to research their question thoroughly before asking it on this site. The help center links to the Movies.SE search engine, but I'm wondering whether users have a responsibility to do that research only in the Movies.SE site or also on other sites.
(In this particular case, I was interested in an answer that relied only on the movies and not on the novels, etc., which was why I came to Movies.SE and didn't go to scifi.SE. Before posting my question, I came across the scifi.SE thread, and my original question contained a list of possible explanations that I found most compelling from the scifi.SE question. But I didn't cite the scifi.SE page and I didn't discuss specific issues I had with their reasoning as I assumed it would be intertwined with the books.)
Motivation for this Question
This meta question discusses the issue in a slightly different regard. It seems to be about simpler questions, whereas I want to ask about complex questions that Movies.SE wants on the site but which have also been asked on other sites. A reason to include these questions was articulated by the founder of Stack Overflow in this blog posting. He talks about how he envisions high-quality posts being the first hits on a Google search. Having good questions with good answers would drive traffic toward the site and away from other sites which might also contain the very same questions.