Albert Barnes Commentary Judges 8:33

"And it came to pass, as soon as Gideon was dead, that the children of Israel turned again, and played the harlot after the Baalim, and made Baal-berith their god." — Judges 8:33 (ASV)

Turned again - Doubtless Gideon himself had no doubt prepared the way for this apostasy by his unauthorized ephod. The Law of Moses, with its strict unity of priesthood and altar, was the divinely-appointed and only effectual safeguard from idolatry.

Baal-bereth - The god of covenants or sworn treaties, corresponding to the Zeus Orkius of the Greeks. The center of this fresh apostasy was at Shechem.