Since they were more identificated with the indigenous people around them which suffered from different abuses from the Spanish, and they desired liberty for those who needed it and, they were not as powerful as the Spanish born in Europe.
If you are referring his defeat at the end against the dragon, that is because of his hubris. He was too proud and believed that he could do it alone without his soldiers. This brings his defeat and he realizes that he will die because of his hubris, after which Wyglaf will take over since he was the only one brave enough to help.
