Why did the Aztec city of Tenochtitlan become one of the richest cities in the world?

The city now known as Mexico City was founded as Tenochtitlan by the Aztecs in 1325 and a century later became the dominant city-state of the Aztec Triple Alliance, formed in 1430 and composed of Tenochtitlan, Texcoco, and Tlacopan. At its height, Tenochtitlan had enormous temples and palaces, a huge ceremonial center, residences of political, religious, military, and merchants. Its population was estimated at least 100,000 and perhaps as high as 200,000 in 1519 when the Spaniards first saw it. Panoramic view of the Zócalo (Plaza de la Constitución), Mexico City, since the Aztecs, the symbolic center. Looking east to the Palacio Nacional. (center) The Metropolitan Cathedral is on the left, the old city hall to the right During the final stage of the Spanish conquest of the Aztecs, Tenochtitlan was besieged and essentially razed. Hernán Cortés understood the strategic and symbolic importance of the Aztec capital and founded the Spanish capital of Mexico City on the site, and in particular rebuilt the Aztec ceremonial and political center as the main square, the Plaza Mayor, usually called the Zócalo.