Rome was made up of many city-states that controlled themselves with their own government. The wealthy and those with ability mattered more than the aristocrats. Merchants and bankers replaced nobility in the upper class. Middle class was the poor workers and the lowest class was peasants.
The art and architecture changed to more realistic art and more colorful. The artist concerned themselves to everyday life and did not paint only religious themes. The architecture went back to classical using domes instead of spires. They wanted beauty and comfort.
The Medici wanted to benefit all of Florence to keep their trust in the Medici family, keeping them in power. This made Florence prosper to entice people to move to Florence.
Italy held onto classical traditions which led its way to attracting artists and the progression of their field. Also Italy had avoided the economic crisis. These thoughts and ideas spread quickly through Europe. Art became so important that the Catholic Church suffered, losing track of their mission, which led to the breaking away from the church and forming the protestant religions