I never understood, why's the moon the most important? I mean, it's just a satelite... it's even less than Pluto u.u'

i think it's because the moon is closest to the earth. main defender, ya'now :)

it's because the author did a self insert and forgot to make things logical. Amount of Deus Ex Moonchina and ass pulls should have hinted to that.

Well, to bring a bit of nerdy logic into it all, the Moon Kingdom has always been in possession of the Silver Crystal. That by itself makes them pretty damn powerful, so it isn't really that weird that they were the ones ruling the galaxy.