Why were the empires in Nebuchadnezzar's image each weaker than the previous one politically?
The empires in Nebuchadnezzar's image became politically weaker because more people were involved in decision-making. Nebuchadnezzar concentrated authority in himself as a despot, but later empires depended on larger groups and consensus, making decisive action harder. Thus each successive empire was politically inferior to the one before.
Les explains that the symbolic image—head of gold, breast of silver, belly of brass, legs of iron, feet of iron and clay—represents great empires. Politically, each successive empire became weaker because the number of people involved in decision-making increased. Nebuchadnezzar, like other great dictators, was a despot and totalitarian, so decision-making was within himself. Later governments, including democracy, may be valued, but getting something done becomes harder with more voices. By contrast, when Christ sets up His kingdom, it will be a kingdom of one with absolute power, no confabs or consensus. Thus all these empires were politically inferior to the one before.