What is ironic in the destruction of the stronghold?
Judges 9:49 (ESV)
49So every one of the people cut down his bundle and following Abimelech put it against the stronghold, and they set the stronghold on fire over them, so that all the people of the Tower of Shechem also died, about 1,000 men and women.
Abimelech destroys not only those who financed his original coup, but also the source of the finance, the temple itself. And thus Jotham’s parable was coming true: Abimelech, the bramble, was consuming the people of Israel with fire.
49 So every one of the people cut down his bundle and following Abimelech put it against the stronghold, and they set the stronghold on fire over them, so that all the people of the Tower of Shechem also died, about 1,000 men and women.