The optimal tactics aren't necessarily that obvious during the first few engagements when you encounter a completely alien force and a way of fighting. And by

The optimal tactics aren't necessarily that obvious during the first few engagements when you encounter a completely alien force and a way of fighting. And by the time you start figuring these things out the Spanish already have thousands of allied soldiers from other tribes that you have subjugated fighting on their side. e.g. when the Inca finally started trying to fight back back in earnest like in the siege of Cuzco the ratio was closer to 1:2 and the Inca were probably too reluctant to engage due to their experience in the initial battles. After that it was already way too late since the empire was reduced to a rump state with limited resources and the balance of power shifted. Same happened in Mexico. Just like in Peru the early engagements for the Spanish were generally considerably easier than the final battles where they had 10s of thousands of soldiers fighting for them. At the end of the day both of those empires were just a house of cards waiting to collapse. Europeans didn't do even remotely as well in less centralized areas. e.g. even against urbanized societies like the Maya who survived for much longer and successfully fended off several expeditions since the Spanish basically had to conquer each city state one by one.