דברי הימים ב, פרק ל״א, פסוק א׳

Following the conclusion of the main events in Jerusalem, a massive wave of spiritual purification swept across the land. Before returning to their homes, the crowds that had assembled in the city set out toward the towns of Judah with a shared purpose [מצודת דוד, ביאור שטיינזלץ]. Along their journey, they actively worked to uproot every trace of foreign worship. They smashed the stone monuments dedicated to idols and cut down the sacred trees that had been planted specifically for these rituals [מצודת ציון, ביאור שטיינזלץ]. Driven by total commitment, they did not rest until they had completely destroyed every single high place and altar [מצודת דוד, ביאור שטיינזלץ].

This campaign of purification was not contained within the borders of Judah. It naturally expanded northward into the territories of Ephraim and Manasseh. This push into the northern kingdom was made possible by a unique historical shift. Hoshea son of Elah, the king of Israel, had previously put an end to the state-sponsored worship of the golden calves. With the royal backing of idolatry removed, the crowds were able to tear down the northern altars without facing any resistance. This same shift in leadership is exactly what gave King Hezekiah the courage to send letters inviting the northern tribes to Jerusalem in the first place, an act that would have been completely impossible had the northern monarchy still been enforcing the worship of the calves [מלבי״ם].