24 God did this in order that the crime against Jerub-Baal's seventy sons, the shedding of their blood, might be avenged on their brother Abimelek and on the citizens of Shechem, who had helped him murder his brothers.
24 that the violence done to the seventy sons of Jerubbaal might come, and their blood be laid on Abimelech their brother, who killed them, and on the men of Shechem, who strengthened his hands to kill his brothers.
24 Violence boomeranged: The murderous violence that killed the seventy brothers, the sons of Jerub-Baal, was now loose among Abimelech and Shechem's leaders, who had supported the violence.
24 that the crime done to the seventy sons of Jerubbaal might be settled and their blood be laid on Abimelech their brother, who killed them, and on the men of Shechem, who aided him in the killing of his brothers.
24 God was punishing Abimelech for murdering Gideon's seventy sons, and the citizens of Shechem for supporting him in this treachery of murdering his brothers.
Matthew Henry's Commentary on Judges 9:24
Commentary on Judges 9:22-29
(Read Judges 9:22-29)
Abimelech is seated in the throne his father refused. But how long does this glory last? Stay but three years, and see the bramble withered and burned. The prosperity of the wicked is short and fickle. The Shechemites are plagued by no other hand than Abimelech's. They raised him unjustly to the throne; they first feel the weight of his sceptre.