Just look at how many different religions and cults there are that claim their version of god is the only true version (and how many people believe in those cults/religions). If the cult/religion is all around you for every day of your life from the moment you were born it's going to be really hard both intellectually and socially to deny the cult and pretty much everyone you know (who still believe).If you believe in something long enough it will become real. It doesn't make it real, it just becomes of method of acceptance where you know nothing else, and you become it, with every last part of you. It will become all you know, and the thought of what is truly real is alien and foreign, and will never cross your mind again.