Many, if not most, were devout in their allegiance to Christianity. Even so, the Founders DEFERRED to the prominent religion and its worldview of the West, Christianity. So much so that they could not think of this new form of government apart from the taming, civilizing influences of Christianity.
And the founders, being aware of the Crown’s interference and use of the Anglican church, made sure to keep the hands of government at bay from religion, its establishments and the free expression thereof. Too bad Congress didn’t respect their judgement.