What does Judges 9:22 mean?

Abimelech came to power by murdering his brothers (Judges 9:1–6). The only survivor of that massacre predicted Abimelech and the people of Shechem would mutually destroy each other (Judges 9:19–20). Abimelech's name means "the king is my father," and his superficial claim is that he's a son of Gideon (Judges 8:30–31).

However, Gideon was never a "king" over Israel (Judges 8:22–23). The text here, as well, does not describe Abimelech in kingly terms. The Hebrew word here is suwr, often translated "ruled," which leans more towards "commanding." In contrast, the Bible uses different words for kings and those who legitimately reign. The Bible does not indicate Abimelech was actually "king of Israel," but that for a time he held sway. He was made king over a group of people, at their request, but that did not make him a real king of Israel.

Even that statement is somewhat surprising. Abimelech was crowned king of the mostly Canaanite city of Shechem. Most commentators suggest Abimelech's literal control only extended to the area surrounding Shechem. Because he was the sole survivor of Gideon's line—other than Jotham, in exile (Judges 9:21)—his influence likely extended to all of Israel, but in name only.

The statement also reveals that Abimelech's power was limited to just a few years. This is not surprising. Abimelech rose to power solely thanks to murderous ambition and the money of Shechem's leaders. His time in power will be destructive and lead inevitably to ruin.