“the remnant of Baal.” That Baal was being worshiped in Judah and Jerusalem shows how insensitive the people of Israel had become to God and His ways. Baal was the top god of Canaan, the Canaanite storm god, and his worship involved sacred prostitution and occasionally child sacrifice. The sacred prostitution was a kind of sympathetic magic in which humans on earth engaged in sex which then was somehow tied into pleasing Baal and getting him to fertilize the earth so there would be a bountiful harvest. Only a blinded heart can worship both Yahweh, who promotes family and godly sexual practices, and Baal, who promotes promiscuity and then occasionally sacrifices the baby that is the fruit of the sexual union. No wonder Yahweh will put an end to Baal.
“idolatrous priests.” The exact meaning of the Hebrew word is uncertain and is debated. Presumably it refers to the priests who had turned to idols, but that may not be accurate.