Religion is excellent stuff for keeping common people quiet.
It’s tough to argue the point with someone who was so great at keeping down the proletariat. The meek, after all, have nothing to worry about since they’ll be inheriting the earth.
Political leaders have a storied history of using religion to maintain social order. For instance, a majority of the key Founding Fathers were deists, and Jefferson was arguably an atheist, but all maintained their Christianity to the public.