What economic and political changes in the city-states stimulated the development of the Renaissance?

The Renaissance represented many things, including wealth, new interests in art and literature, different ideas from the Church, and a brief moment in which people can finally stop dying in mass. Ironically, two long-term causes succeeded because of people dying. After the Crusades, the Europeans didn't go home empty-handed. They had information of the Greeks, Romans, and their art/philosophy/lifestyle. This lead to developing art, philosophies, and literature of the Renaissance, while the Europeans also began trading with other regions to increase trade. The second main cause was the reappearance of the Black Death. After the plague, there was a sudden surplus of food for the survivors. The average price for food soon dropped, and people were able to buy more. Although bartering was still a common practice, richer people practiced currency. Soon credits were moving, and banks were created. This new boost to the economy brought attention upon things that weren't previously valued (such as tiles), and then sprang forth specialization. Families were able to control city states through economy, and they will soon become the "Lords" of the Dark Ages. They would attack each other for more land and have also developed an interest in owning artworks.