Empire, Exile, and Monotheism

Isaiah says more about the uniqueness of God than any other Old Testament writer (especially Isaiah 43-45). Why did Yahweh wait so long to say this?

Did he perhaps have to set up empires, deliver His people into exile, and then send them back before He could persuade the world that there was One Lord, Savior, Lawgiver? Was the exile and restoration somehow the first real proof of monotheism?