Baal was worshipped in many local manifestations. The patron deity of Shechem was Baal-berith, which means Baal/Lord of the Covenant.
What makes this so ironic is what we read in Judges 8:34, that Israel did not remember the Lord their God, who had delivered them from the hand of all their enemies on every side.
So In worshipping Baal-berith, a god whose very name includes the word for covenant,
Israel forgot their covenant God, who had delivered them. Furthermore, Shechem was the very place where Israel had renewed their covenant with the Lord, swearing never to worship the gods of the land (Joshua 24:1–33). Israel did not remember the Lord their God. They turn to idols.
33 As soon as Gideon died, the people of Israel turned again and whored after the Baals and made Baal-berith their god.