Albert Barnes Commentary 2 Kings 11:3

"And he was with her hid in the house of Jehovah six years. And Athaliah reigned over the land." — 2 Kings 11:3 (ASV)

And Athaliah did reign over the land - In these words, the writer dismisses the entire reign of Athaliah, of which he scorns to speak.

We gather incidentally from 2 Kings 12:5–12, compared with 2 Chronicles 24:7, that Athaliah used her power to establish the exclusive worship of Baal throughout the kingdom of Judah and to crush the worship of Yahweh. She stopped the temple service, gave over the sacred vessels of the sanctuary for the use of the Baal priests, and used the temple itself as a quarry from which materials could be taken to construct a great temple to Baal, which rose in the immediate neighborhood.