Ancient "Judaism" was without one clear view of God. The ancient hebrew texts hint towards a henotheistic, monolatristic, and sometimes even polytheistic viewpoints. Psalm 104, for example, is remarkably similar to the Hymn of Aten, and clearly sun worship. Josephus, the famous Jewish Roman historian, himself was a henotheist. It's quite possible Jews didn't become hardcore monotheists until Christianity was born. I'm of the belief Judaism stems from Atenism, which was the world's first recorded henotheistic faith. The world's first monotheist religion was Zoroastrianism.