Partly because they were not contented with those idols which the Canaanites worshipped, but either themselves invented, or they borrowed from other nations, many new idols and kinds of idolatry; and partly because as their light was far more clear, their obligations to God infinitely higher, and their helps and antidotes against idolatry much stronger than the Canaanites had; so their sins, though the same in kind, were unspeakably worse in respect of these dreadful aggravations.
Related Commentaries of 2 Kings 21:9
2 Kings 21:9
9 But they hearkened not: and Manasseh seduced them to do more evil than did the nations whom the LORD destroyed before the children of Israel.