Yesterday I said that "2nd Isaiah" probably came to his confession of one God along with other Jews in the Babylonian Exile. Upon further reflection I like to think, rather, that he was a brilliant, unique, religious thinker. (I thought of Einstein in science.) In 2nd Isaiah's own deep prayer and individual meditation, he becomes convinced that there is only one God. He feels impelled to tell others. He is bold enough to put in the mouth of God these words: "Besides me there is no god."
For 2nd Isaiah the one God is responsible for the entire cosmos, the God of the natural world and the God of history. This one God has the care of all the nations (gentiles) and intends to save them all. 2nd Isaiah links monotheism with universal salvation.