I think what the OP is asking about is the puberty of spiritual belief, in where beforehand belief in the sacred was infused into everyday life and experience, and afterward belief blossomed into a divorce from that and into a sense of separation from the sacred.
In effect, one believed in the magic of Santa and after the reality of his nonexistence hit home then one believed in the IDEA of Santa (or didn’t).
The god of the (generally) Old Testament was more ‘real’ in the everyday lives of people, just like the Greek gods were: always helping or meddling and pulling pranks and talking to so-and-so, and causing catastrophes. He was a part of everything, all the time, and there was NO CONCEPT of the world or man as separate. You have to really take that last sentence in to understand what a critical change it was to believe God as separate.
The god of the (again generally) New Testament is one who is definitely ‘separate’ from man and the world, divorced from us if you will. Wherein we have free will and are always ‘guilty’ for being separate from him.
Old god=no guilt, we are one with him. New god=guilt, we are separate.
As you can imagine, the mythic stories change quite dramatically between the two.
But the Bible, and other religious texts to boot, are jumbles of myths. So you see this separation/creation myth in both Testaments. But what caused the great switch in belief? Well, short answer, the switch from agrarian life to city/state life.
The New Testament was shaped more by the mythic system created by city/states (“Mess-o-potamia”). The Old T was less organized and more of a collection of popular ancient myths.
Then, added to this mix was the political consideration of Rome and how THAT shaped the Bible. (And you thought only modern times had angry activists!)
The Bible (mainly the New Testament) became a good political pamphlet (they had lengthy pamphlets back then). One of the problems Fundamentalists have today is the application of this 2-century old political stuff to the political stuff of modern day.
It don’t fit. So, they pound it and twist it until it do.
Example: The controversy over Mel Gibson’s interpretation of Christ’s life. One of the complaints about it is its focus on violence. Well, which is more important, the literal violence that Christ had to experience, or the spiritual teachings that he gave? Fundies focus on the violence, the blood, the profane. (Mel has said he wanted to focus on this shocking aspect, which it is…to US! But, do you think that the violence was shocking to people back then when crucifixions were a common spectacle?)
Spiritualists focus on the meaning, the sacred. They try to learn about the IDEA of Santa and apply that to their lives while Fundamentalists are off to the North Pole looking for him.