The Iroquois had past ties to both the English and the French, and the French had agreed to act as the authority between signatory tribes.
Actually, the civil war make their relationship became much worse.
Because of the civil war, the ally has to lose a lot of resources for war supplies and equipment. This led to a situation where the allies no longer able to pay the treaties that they promisd to pay to the Sioux, which eventually ended up in conflict between the two group.
The best options would be that" <span>E. Disease brought by the Spanish devastated the Inca population</span>" and "C. The Inca did not have the modern weapons and firepower that the Spanish did", since it was this superior weaponry that allowed most for their demise.
I'm guessing he was old lol