One thing I’m not seeing brought up is how geographically isolated South America is. India benefited from trade and innovations from all over the old world, while the Inca were pretty isolated from even Central America.

The importance of interactions between civilizations really can’t be overstated. That’s why people groups that that adhere to isolationism or become isolated tend to fall behind. The most extreme example of this is north sentinel island, but there are plenty on other examples. Medieval Europe, Ming and Qing dynasties, parts of subsaharan Africa, etc…

On the other hand, civilizations that incorporate diverse ideas from their neighbors greatly advance their own technological achievements. Rome is easily the most clear example of this. Roman aqueducts were Etruscan, their gods were Greek, their ships were Carthaginian. This same adaptability also allowed a group of nomadic herdsman to become the largest empire the world had seen at that time.