odin1

So, instead of learning having literally become a religion, it filled the psychological void once occupied by religion.

Let's check out the rest of the scenario:

(a) Religion was once part of their normal cultural development
(b) Religion was abandoned
(c) The absence of religion represented a psychological deficit to their survival capabilities
(d) To compensate for the deficit, they devoted themselves to learning

The question you've raised is: "What could have caused them to abandon their religion?"

Is that right so far?