And I reached the conclusion that period of time that gets the closest is the world post world war 2. The post-apocalyptic reality of the Fallout world is much different than ours and requires the right lenses. However, thinking about it later made me realize that I was scrutinizing him (and his religion) through my own, real world biases. Replaying Fallout 3 after a lot of time myself, I was unimpressed by confessor Cromwell's ideas. Browsing these forums the common consensus on Fallout 3's religion seems to be that it's really goddam stupid.