Despite their large numbers, the Inca forces could not bring their full numerical advantage to bear all at once.

“the annual cycle of planting and harvesting the crops you need the men on their farms to do that because if they're not there then you face a very hard year coming up if you don't have enough crops set aside to get you through the winter and the following year so for all those reasons the NK yes those huge numbers weren't able to really overwhelmingly apply them at the same time if they caught perhaps”