Because the fanfiction of a fanfiction of the religion of your ancestors with all the names filed off and the all gods replaced with one single Mary Sue deity who became crazy and schizophrenic as a result is the one true religion, obviously. Ultimately it doesn't matter much, the damage of Christianity has already been done and the worst traits of Christianity have been sanded down and improved by thousands of years of exposure to European culture, so having a strong "team affiliation" might help with the pending societal collapse, but you might prefer not to have the other members of "team monotheist" in your team when things turn nasty.