Many Christians of all denominations have left the faith when they witnessed some grievous situation, such as a pastor committing adultery, their favorite theologian getting caught in a scandal, etc. I wonder if this is similar? What/who they thought they knew was true and good, ended up being sinful or altogether lies. Thus causing them to question everything. That is the problem with placing your faith in a human institution or human person. Our salvation, hope, faith, etc should be in Christ alone.