>>212963067 (OP)He was the godking of his own religion with him at the head. He knew Eru existed, but in his mind he was the only arbiter of Order left to impose it over middle earth. Plus magic was fading, but his industrious ways allowed it to stay in the realm through his ringcrafting.
So what does the Sauron religion look like? I don't think he cared about what you believed in, only that you obeyed and remained subservient. There wouldn't be churches, mass, sacraments or anything like that, but there would be factories, very little nature, hierarchy, and absolutely no true free will. Essentially it would be some weird cyberpunk dystopia but in a medieval setting, one single conglomerate mega-corporation and Sauron is the permanent CEO, with all the middle earth creatures being doomed to be wagies for life or killed.