SS, Pratchett spends a large part of the book building up the image of "Om" and the Mosaic religion he supposedly inspired. The plot of the book is that when Om tries to manifest for a "smiting", he can only manage tortoise form and finds there is only one true believer left, a brother named Brutha. Without Brutha he'd be back to elemental form, so to speak. The start is quite funny, where the god talks to Brutha in tortoise form, Brutha assumes it is a demon and goes running to a senior monk, a dirty old man who's experience with demonic seduction is somewhat more seductive than a tortoise, for advice on how to handle it...
The man at the top of the Omnian religion is a senior Bethelite JC kind of guy, who like Rutherford turns the rules of the org around to help himself to the position of head honcho.
"You've got the brain of a four-year-old boy, and I'll bet he was glad to get rid of it."
- Groucho Marx