Complex sentence: Nebuchadnezzar's experience of God's power was personal, but the lesson is for all mankind; the issue is the relationship between heavenly and earthly power: the king's power on earth is not denied, but it is subordinate to the power of God.
Split into simpler sentences: Nebuchadnezzar's experience of God's power was personal, but the lesson is for all mankind. The issue is the relationship between heavenly and earthly power: the king's power on earth is not denied, but it is subordinate to the power of God.