It's interesting to think of religion as a societal tool that has co-evolved along with humanity. Societies with more beneficial religions would prosper and societies with less beneficial religious would die out. It's thus no surprise that the religions that survived until the present day promote human survival. For example, it's no accident that most major religions heavily encourage their followers to have a lot of…
In my view, early bands of humans who weren't following a charismatic leader, who weren't following a strong religious practice, were killed off by those bands of humans who did follow the word of a charismatic leader who assured their followers that the divine itself were guiding their decision making. Fast forward though millions of years of evolution, and of course we are predisposed to religion, to xenophobia, to answering some call of duty and dying in someone else war. Our cultist ancestors killed off anyone they came across who didn't follow with this program. This behavior of humans hasn't even gone away today, its so entrenched.