Better Health Through Less Flavor
Like I said, if I have to tell you why something with the word OPERA makes sense in conjunction to WAGNER, its lost on you.
I'm fairly certain that the term "space opera" was inspired by the early sci-fi pulp writings, not the other way around. It's a peculiar expression of English, not some kind of decree that all space war stories in cinema need to be accompanied by a certain genre of music.
(...and if I were to be especially anal about it, I could think of maybe two or three occasions of the above where the romantic-opera style of music was used to accompany a Germanic legend-type story, and one of them was directly inspired by the Ring. None of them had singing, though it would have been neat if one did.)