[quote]So they work together during wars, and have the capability to conquer the galaxy when working together, but haven't? This doesn't make much sense to me.[/quote]

It is the same thing as the Chinese (Nationalists and Communists) versus the Japanese during the 1930's. Differences are put aside for the greater threat. A second, possible negative trait is their largely antiquated technology. I'm not opposed to using that one.