Europe was technologically advanced but lacked in state capacity. The Aztecs and the Maya were the opposite.

Sanitation is a literal stone age technology, originally developed by societies we have very little evidence of. It doesn't require technological sophistication — only a government capable of and willing to administer it.

European middle ages were characterized by the lack of state capacity. Cities and trade declined after the fall of the West Roman Empire. Governments became weak and incapable, and the society was structured around regional warlords and their personal relationships. But technology kept moving on. While European societies had limited resources, they could do things their more capable predecessors could not.

And then, towards the end of the middle ages, states started consolidating again.