Every time the king's name is mentioned in Judges 3:12–17, he is also identified as king of Moab.
But after Judges 3:20, the author no longer does this. It is as though the man who was a somebody for eighteen years is all of a sudden a nameless nobody.1
12 And the people of Israel again did what was evil in the sight of the LORD, and the LORD strengthened Eglon the king of Moab against Israel, because they had done what was evil in the sight of the LORD.