Abimelech, and the companies that were with him, rushed forward, and stood in the entrance of the gate of the city: and the two companies rushed on all who were in the field, and struck them.
In other words, he's an outsider. We ought to be serving Hamor and his family, let them be the kings. And he said to God the people were under my rule, because I can really do a good job here, you know. Who's Abimelech? And so he said if you would just commit yourself to me I would remove Abimelech.