My deduction would be why a lot of time Demons don't seem to bother people that are not from the Abrahamic religions is due to this kind of things happening.

To explain it in easier terms, these beings, the Demigods, they were enjoying the adulation of the Aztec and Incans, they are given fresh human sacrifice, suddenly come another factor, took their people away, took away their adulation, took away the sacrifice that they were enjoying and now their people also betrayed them by now praying to the God in Christianity. So these Demigod, these beings of course will be extremely pissed off with the faction that took everything away from them. Hence unit now they are still looking for payback.