This is kind of crazy, but hear me out. Between Zoro's King of Hell, Tar D. Eris on Imu's shield, and other narrative evidence, a lot of people, like me, believe Hell is a real, visitable place in One Piece.
What if that's where this all started? What if Joy Boy/Luffy's Soul, and the souls of the other Straw Hats/big players... broke out of Hell before things really kicked off? That would be fucking wild.