My theory:

So, it turns out, the actual original legendary Zodiac Weapons that you went through all that work recreating? Yeah, Godbert Manderville has all of the originals. Which he made in the first place. He is so impressed by your craftsmanship, that you've proved yourself to him as a Manderville Man (or Manderville Woman!), and he agrees to give you the original, powered up version of your replica, with one condition: A true Manderville Man (or Manderville Woman!) is so amazing that they can even bend luck to their will. You must win every game in his casino, the Manderville Golden Saucer, to show your mastery over luck itself, and then beat every major NPC in the game at Triple Triad to show just how awesome you are, culminating in a final epic (clothesless) showdown between you and Godbert himself. Only then is the truth finally revealed: Godbert was the Zodiac Braves. All of them.

Once you win at everything, he gives you the true Zodiac Weapon. And then he makes another, just because he can.