People convince themselves of false truths because of cognitive dissonance. When a verified piece of information threatens someone’s world view or self- concept, an uncomfortable tension occurs from having two conflicting thoughts, and the brain works to avoid discomfort by resolving the conflict. Because the actual facts cannot be changed, one either has to change their own mind, or continue to accept the false truths through reinterpretation and irrational behavior- and the latter is typically much easier to do. Source