Then the king of Assyria commanded, “Send [the new inhabitants of northern Israel] one of the priests whom you carried away from there, and let him go and dwell there and teach them the law of the god of the land.”
2 Kings 17:27

The priests of Israel were already apostate because of Jereboam's false religion and temple, so his teaching did little to correct the problem, probably only changing their vocabulary. The fear of YHWH will lead you to desire his laws, but that desire must be met by qualified teachers. A teacher who knows part of the truth (the Ten Commandments or Torah or the New Testament) is good, but a teacher who knows the whole truth (Genesis to Revelation) is much better.