The main factors which led to the collapse of the Aztec Empire were not internal or psychological. The main factors had to do with Spanish technology and the Spaniards’ ability to find nations that had been subjected by the Aztecs and were eager to fight against them.
However, it can be said that there were internal, psychological factors that helped contribute to the collapse of the empire. The main one of these was the uncertainty and nervousness caused by the appearance of the Spaniards. The Spaniards fit all too well with the legends about the return of Quetzalcoatl. This led to some fear, but also to uncertainty because the legends were not very specific about what Quetzalcoatl would be like and what he would want. This uncertainty helped to weaken the empire and make it more susceptible to collapse.