Albert Barnes Commentary 2 Kings 21:9

"But they hearkened not: and Manasseh seduced them to do that which is evil more than did the nations whom Jehovah destroyed before the children of Israel." — 2 Kings 21:9 (ASV)

During the long reign of Manasseh, idolatry in all its varied forms took hold of the Jewish people to a degree never known before (compare to Jeremiah 7:18, 31; Ezekiel 23:37; Zephaniah 1:5). The corruption of morals kept pace with the degradation of religion (compare to 2 Kings 23:7; Zephaniah 3:1–3; Jeremiah 2:8; Jeremiah 5:1).