@freemo Just for kicks here's some further evidence for you.
"In the seventh year, in the month of Kislev, the king of Akkad mustered his troops, marched to the Hatti-land, and encamped against the City of Judah and on the ninth day of the month of Adar he seized the city and captured the king. He appointed there a king of his own choice and taking heavy tribute brought it back to Babylon."
So there was a king in Judah. It's possible they were not connected to David. But that doesn't matter.