[antiraza]

I'm not certain I understand where the problem is? Trades are learned by apprenticeship. Knowledge is learned by oral transmission. As the previous commenter said, this has been normal for most of history, and frankly is still the case many places around the world. Literacy is _new_. Even when literacy was emerging, it was likely that a mason or a carpenter was not of a literate class and they learned the same way generations before them did: apprenticeship and oral knowledge transmission.

[mmooss]

We're talking about adminstering and leading large-scale empires, which is enough of a difficulty, and doing it in the special circumstances of the Incas. And as part of that, developing and advancing these technologies and all the precursors to it - culture, education, skills, technology itself, and political support for it, all on that large scale.

If you think that's easy or normal, consider that it is hardly ever done. Few accomplish what the Incas did, much less with their challenges (see the OP regarding those). For an example, look at China in the mid-to-late 19th century, a place with far more advantages, as they tried to adopt technology.

Edit: From the OP:

"... they managed to create the largest empire ever seen in the Americas – a sprawling two-million-sq-km civilisation that extended across parts of modern-day Colombia, Ecuador, Peru, Bolivia, Chile and Argentina – encompassing as many as 12 million people and 100 languages. It was roughly 10 times the size of the Aztec Empire and had twice its population. Remarkably, the Inca managed to forge this vast society without the wheel, the arch, money, iron or steel tools, draft animals capable of ploughing fields or even a written language."

[alephnerd]

They used Quipu to catalog most administrative information (taxes, census, military, etc) - https://en.m.wikipedia.org/wiki/Quipu

Quipu's are actually pretty cool - it's basically a proto-flamegraph and could even potentially be used alphabetically, but we wouldn't really know as there just aren't that many left after the brutal Spanish invasion of the Inca empire and the subsequent inquisition.