Seems to also imply Joyboy wasnt a king at all. He was simply the first pirate in that clan. Seems Davy Jones may have been the king of the Ancient Kingdom.
The 20 Kings revolted and we are in the cureent predicament. I assume this is also why Rayleigh says to not rush in coming to a conclusion about certain things regarding the Void Century.
Given how different Blackbeard and Luffy are, I assume Davy Jones was oppressive and the D. Clan are the cause of their own demise in a way