To many of the faithful, leaving the faith is no only unthinkable for themselves, but it is unthinkable that it happens to others.
Usually, believers assume that when someone leaves the faith it is because they were treated badly or abused within the faith or by parents. In my experience, this is not usually what happens. It is instead an intellectual process.
Dan Barker, a former evangelical preacher, has become one of the country’s best know atheists. Apparently, he was a quite successful in his preaching career. In the link below, he explains the process he experienced.
During most of his Christian life he was a literalist. Bart Erhman, the prominent New Testament scholar and former literalist, says literalists develop a bag of tricks to avoid the notion that the Bible has contradictions. So, when the Bible has various versions of one story like the birth of Jesus, the literalist explains why all version are true. It’s just that different people knew different things.
Barker’s first problem came when he learned there were sincere Christians who did not believe in the literal Adam and Eve. After he came to see Adam and Eve as metaphor and as literature rather than history, he began to wonder about the other stories and Biblical characters. Eventually, he concluded the entire Bible is literature not history.
Barker’s journy is typical of how people become nonbelievers. As the number of such people grows, we will hear more such experiences.