Those who won't ride rough-shod over doubt or questions, even though they know it might save a lot of grief if they did. Those who are most effective provide a safe place for struggle, questions, growth. Just as the disciples provided a safe place for Thomas. But that requires a great deal of love. The sort of love cult leaders refuse to offer.
Cult leaders are unable to take the risk of allowing people to think for themselves.
They demand absolute unquestioning obedience to their interpretation of the Scriptures, even though they often take a small portion of the gospel and turn it into the whole package, overlooking Jesus' concern for compassion and justice and healing. Perhaps not the resurrection. He may have been perfectly able to accept that someone had stood in the midst of the disciples. But perhaps he needed to be certain the one who was raised from the dead on the Sunday was the same one who was crucified on the Friday. Perhaps Thomas wanted to verify that the crucifixion and resurrection of Jesus wasn't some cruel hoax perpetrated on a desperate humanity.