I have long suspected that your “buyer’s remorse” proposition is true for most believers. Given the breadth of the effect religious belief has on the business of living one’s life and the seeming competition for being more fervent than the next guy in the pew, I suppose it is to be expected to one degree or another.
The mental distress of coming to terms with the realization that you have wasted some part of the one most valuable commodity one has (days of life) has to be incredibly difficult to bear.
The point is NONE of it happened. Any more than any of the “miracles” and such Christianity plagiarized from predecessor religions happened.