European conquest was not just a result of superior firepower In tact, the most powerful weapon of the Spanish conquerors was not a conventional military weapon at all.
It was the germs such as those of smallpox that they carried on their person. Smallpox in particular proved a deadly killer. Once Introduced, It spread deep into the continent, ahead even of any European reaching there. It killed arid decimated whole communities, paving the way for conquest.