Our brain's meaning making requires a certain level of religiousity to understand/make sense of the world. With the advances of science over the last hundreds of years the old religions can no longer provide us with some of the functions they used to. So we now seek religion in other things.

This is a good 50hr+ investigation into meaning making, and and attempt to resolve our meaning crisis: John Vervaeke: meaning crisis

There may have been cities along the Amazon (since collapsed and eaten by the Amazon), with a population of more than the equivalent of Europe at the time.