How did the ideas of each of the major enlightenment thinkers challenge absolute monarchy?

These thinkers valued reason, science, religious tolerance, and what they called “natural rights”—life, liberty, and property. Enlightenment philosophers John Locke, Charles Montesquieu, and Jean-Jacques Rousseau all developed theories of government in which some or even all the people would govern.

Explanation:

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Soviet Union began a slow process of democratization that eventually destabilized Communist control and contributed to the collapse of the Soviet Union.

A number of events and uprisings in the 1980 are led to the collapse of the Soviet Union. ... Last, in the Soviet Union, the failed August Coup in 1991 led to the end of the Communist party in USSR. All of these events led to the end of communism and the making of a democratic Russia.

it collapsed on  December 26, 1991