King Nebuchadnezzar would learn that the world doesn’t revolve or depend on him. He would also learn most valuable lessons about his future and the world’s future. God permitted Nebuchadnezzar to have some dreams which troubled him deeply to the point that he could not sleep.
As a result, Daniel gives Nebuchadnezzar a future history lesson from which all the people of Daniel’s time and our time can learn so that we can know God more intimately.