I'd still suggest the overlap isn't incidental. Religions need stable or expanding societies to procreate. So ideology that leads to stable or expanding societies is strongly selected for. Religions with written texts have surprisingly low mutation rates in their ideology, but when conditions begin to favor different behaviors to promote stability, polygamy for instance, the ideology changes quickly.

As a reference to my biases, I'm a theistic agnost, I don't know, but I believe. The life of pie or secondhand lions explain the why pretty well.