Albert Barnes Commentary 1 Kings 14:9

"but hast done evil above all that were before thee, and hast gone and made thee other gods, and molten images, to provoke me to anger, and hast cast me behind thy back:" — 1 Kings 14:9 (ASV)

Above all that were before you—that is, above all previous rulers of the people, whether judges or kings. Until now, none of the rulers of Israel had established the idolatrous worship of the ephod, teraphim, and similar objects (Judges 18:17) as a substitute for the true religion, nor had they sought to impose an idolatrous system on the nation.

Gideon’s ephod became a snare contrary to his intention (Judges 8:27). Solomon’s high places were private, built for the use of his wives and not designed to attract the people. Jeroboam, however, was the first ruler who deliberately set out to turn the Israelites away from the true worship. He established a poor counterfeit of it and succeeded in making it the religion of the great mass of his subjects.

And have cast me behind your back. This is a very strong and rare expression, occurring again only in Ezekiel 23:35, where it is said of the Jews in general, shortly before the captivity. The expressions in the marginal references are similar but less severe.