How Did Athens Change Government

In the distressed world of the fifth century BC, Athenians struggled against a series of tyrants and their greatest rival to create a new form of government. After rule of tyrants of the aristocratic class and a struggle for power, Cleisthenes sided with the common people of Athens and brought the first democracy to existence. From then, democracy developed and flourished. As Athens was building the foundation of government, they had to live with the threat of war from Sparta, their greatest rival, and the Persian Empire. But since democracy had already taken route, it was soon to prove that in the long run, it could defeat the strongest forces.
While watching this story, I was fascinated how a single man managed to completely change government.