Charles Ellicott Commentary 2 Kings 18:12

"because they obeyed not the voice of Jehovah their God, but transgressed his covenant, even all that Moses the servant of Jehovah commanded, and would not hear it, nor do it." — 2 Kings 18:12 (ASV)

Because they obeyed not ... —Thenius calls this remark, which properly belongs to the historical abstract from which the compiler drew the narrative of 2 Kings 18:1–12, “the theme” which suggested the reflections of 2 Kings 17:7–23. They may have been suggested by passages of the Law and Prophets.

And all. —Omit and, with all the versions. “All that Moses ... commanded” is in apposition with “his covenant.”

And would not ... do them. —Literally, and did not listen, and did not act.