Specifically, why did God use Europeans – themselves infected with sexually transmitted diseases – to educate indigenous people in Central America, South America, and North America about the moral imperative for strict monogamy?
The indigenous people weren’t infected until the Europeans brought the diseases. It looks as though Christianity was a cultural adaptation to an invisible part of the environment.
The indigenous people might have initially thought that it was merely a strange custom. However, perhaps they should have compared strict monogamy as a moral and religious imperative with an enormous bomb shelter. In a world with enormous bomb shelters, there may be extremely powerful bombs. In this case, the bombs are invisible pathogens.
Enormous bomb shelters – although not themselves frightening – should be a signal that there is something extremely dangerous that we need to be aware of.