God would be superfluous as an explanation of religion's origin, if the theist grants the validity of an intermediary naturalistic explanation because adding that God is still needed to have created the whole universe as the first causes adds nothing. That would be an empty appeal to an initial miracle. All the explanatory work would be done by the naturalistic explanation of the history of religions.

And you'd have two explanations of religions: the naturalistic, sociological, historical one, and another that adds a supernatural pseudo-cause. Especially if the theist concedes the former as far as it goes, the latter is more trouble than it's worth since it adds an ontological category without explaining anything. Appeals to miracles aren't explanations.

The bad theology would belong to the theist, not to the atheist. When everlasting torment in Hell for God's creations is on the line, the theist would have to explain why God gives fuller proof of his existence to some, via direct, mystical visits, and leaves most with the imperfect, ambiguous antenna that's susceptible to a naturalistic, atheistic explanation.