I'm not sure I quite follow, but the "all at once" phrase may be a large part of your difficulty accepting the natural explanation for belief in gods.
I was trying to illustrate the fact that inferential reasoning is common, even among other animals. Primate studies have demonstrated they are very similar in their ability to impute motives and formulate opinions about personalities and anticipate behavior. This is sometimes part of what is called social cognition. In short the ability to conceive and retain an impression of another personality. For humans, having the added ability of complex language, we pass on detailed concepts, to get transmitted communally, eventually changing and growing in sophistication with the additional input of more imaginations. We can have real emotions about imaginary characters. Fear, affection etc.
So, what I'm getting at is there is nothing "all at once" about it. Human religious development grew from simple assumptions of agency involved in the otherwise unexplainable movement into complex rationalizations of how to appease these agents. The agents are mental constructs that offer comfort or fear.
Monotheism is a very late invention in our species. Some would say it is an unworkable one. Persians and Jews (and Egyptian Atenism) found it difficult to attribute all the good and bad to a single powerful praiseworthy entity. Hence the concept of an ultimately good and an ultimately bad god in eternal struggle. God/devil. True monotheism probably never existed.