He might easily flee, having the advantage of the hill and other accommodations for flight, and because the people were not forward to pursue a man whom they knew to have such just cause and great provocation to speak, and so little power to do them any hurt. Beer; a place remote from Shechem, and out of Abimelech's reach. There were divers places of that name.
Related Commentaries of Judges 9:21
Judges 9:21
21 And Jotham ran away, and fled, and went to Beer, and dwelt there, for fear of Abimelech his brother.