For me, the core principle should be this: if you argue characters should or shouldn't behave a certain way based on comparison with a point in earth's history (unless your intention is specifically to recreate that period (such as during a Call of Cthulhu 1920s era game for example)) you're doing it wrong. Our characters have no notion of earth or its history. Their motivations come from their world and their experiences.
If the Taniel church opened a casino, I wouldn't argue that they shouldn't do it because medieval European churches wouldn't have stood for it, I would argue that a god of Order wouldn't stand for people profiting from chaos. People have already pointed out numerous inconsistencies with earth history of a comparable time (but overlooked sewers, really history buffs? Stop slacking

Geas lore does have holes in it, but so does ours. History rarely more than a one sided opinion of events, some bits are just lost all together. Even the concept of a strong universal Christian church is rather at odds with history which is replete with multiple cults, factions, phases, and heresies. Some were tolerated, others were persecuted. The prevailing church/religion/philosophy was generally the one favoured by the rulers or at least the people likely to make your life miserable if you didn't agree with them. Holey lore is a good thing though. It allows the players to have an impact on the society they're a part of, as they should. PCs are exceptional characters rather than average. They should be trend setters and change makers, the outliers, the memorable, the freaks, the noteworthy!
One thing I will always find peculiar though is people trying to play atheists. People trying to stay out of the affairs of the gods is fine, but people who don't believe in them are just deluded. I mean...they literally bring you back to life. Angels and demons are running around. Their existence is incontestable. It'd be like not believing in chairs. Their nature is perhaps debatable, at least until someone interviews one of the deities I guess
