The Neoclassical period was about looking back to the classic (Roman and Greek civilizations) as guides. Everything became simplified and had a reason to do so. People began to ask "why" they are being ruled by a king, why they couldn't climb the social ladder in life, why some were slaves, some were free. In the America's, colonists considered the benefits of declaring themselves independent of Great Britian. It was not about leaders glorifying themselves at all.
Since ancient Greek and Roman architecture stood the test of time, it was looked upon as a guide or the "rules" for architecture.