Why did pre-modern states adopt Big-God religions?

Over the past two millennia successful pre-modern states in Eurasia adopted and cultivated Big-God religions that emphasize (i) the ruler’s legitimacy as divinely ordained and (ii) a morality adapted for large-scale societies that can have positive economic effects. We make sense of that development by building on previous research that has conceptualized pre-modern states as maximizing the ruler’s profit. We model the interaction of rulers and subjects who have both material and psychological payoffs, the latter emanating from religious identity. Overall, religion reduces the cost of controlling subjects through the threat of violence, increases production, increases tax revenue, and reduces banditry. A Big-God ruler, who also is a believer, has stronger incentives to invest in expanding the number of believers and the intensity of belief, as well as investing in state capacity. Furthermore, such investments often are complementary, mutually reinforcing one another, thus leading to an evolutionary advantage for rulers that adopted Big-God religions.