If you read enough stories of de-conversions (and there are lots of them), you will come to the conclusion that no theist has the slightest clue what would cause them to doubt or lose their faith. Prior to the events leading to a crisis of faith, theists cannot conceive of anything that would change their minds. This, I believe, is due to the extreme compartmentalization needed to cling to faith in the face of cognitive dissonance.
A couple of characteristics that seem likely to lead to a loss of faith are Intelligence, Curiosity, and a Love of Learning. Theists who possess these characteristics in abundance will have a harder time denying reality in the long run.
A couple of characteristics that seem likely to lead to a loss of faith are Intelligence, Curiosity, and a Love of Learning. Theists who possess these characteristics in abundance will have a harder time denying reality in the long run.