what I want to know is what is the advantage given by religion(s) that allows it to pesist.
Theists often have more offspring. I think it was Stephen Ben Yeshua who argued convingly with me on this site that his beliefs were evolutionarily superior to mine because he had many more offspring.
Christianity in particular emphasises very early marriage, traditional family structures and the indoctrination of children into the religion.
IMO religion also an advantage in battle. Those who are fearful of death, ironically, often do not fight as well as those who believe a God is assisting them and will provide them with paradise if they die for the cause.