I'm not sure it would have done much to change the trajectory of Judaism or monotheism, really. The survivors of Judah would have been carted off to Nineveh, where, faced with the need to stay together as a nation in exile, they would have codified the tenets of their religion a century earlier than OTL (under Josiah and then in Babylon). Hell, considering that Samaria-Israel had only been eradicated a decade earlier they'd probably come back into contact with the "Ten Lost Tribes" and strengthened Judaism as a whole.
Under this new Judaism Hezekiah would likely be seen as the OTL of Josiah (as a reformer who came too late to save his country), and King Ahab of Israel would have been seen as even worse than historically, and the cause of God's wrath against the Israelites+Judaeans.
Might even see the Babylonians playing the role of the Persians in this timeline, seeing as the Israelites would no doubt be rather grateful for being allowed back into their native land.