Which factors enabled the Spanish to defeat the Aztec and the Inca?

The Spaniards' superior weapon technology and immunity to European diseases enabled the Spanish to defeat the Aztec and the Inca. When they came over to the New World, they carried over diseases like the small pox and devastated the population, leaving only few healthy warriors to combat the cruel conquistadors and their men. Because the Natives lacked the guns, which facilitated the killing process, their subordination under the Spanish rule was inevitable.