Democracy, or power by the people. This was founded in Ancient Greece and is still used today.
Initially, other rulers in Europe were somewhat pleased that the Bourbon monarchy in France was being reduced in power by the effort to make it a constitutional monarchy. But as the French Revolution proceeded, other ruling houses and nobles in Europe felt the threat that such revolutionary fervor could pose to their own positions, and were ready to fight to stamp out the Revolution. Revolutionary France went to war against those other nations, and when Napoleon took over power in France, he continued those wars and won conquests. Napoleon brought the Civil Code that contained some of the basic ideals of the Revolution to other territories that his empire controlled. Even after Napoleon was defeated, the ideas of liberalism that the French Revolution had unleashed remained as a powerful force, and the 19th century would see a recurring series of revolutionary movements across Europe.
Answer:
The basic causes of the decline of the landed aristocracy are clear enough: the collapse of agriculture and the march of democracy. The first was the more important