I like to think about religions, from the point of view of when they were being formed. Take Christianity when it morphed out of Judaism. Now forget all the virgin birth and fulfilling of prophecy stuff, that's just to distract the sheeple masses. Okay, so get down to the roots of why you would create a religion where a Devout follower of Judaism (Jesus) would just up and create a new religion where the rest of the world from that point forward was to believe in him, or burn in hell.
Anyway, what I get from it is if you understand Judaism or Islam, they are fairly difficult religions to follow/practice, assuming you obey all the laws. That's pretty much what those religions are about, following the laws of God to get into heaven. Then along comes Christianity, and now you don't have to follow any of the OT laws. All you have to do is say, "I believe in JC, blah blah blah" and give 10% of everything you make to the church, and magically you get into Heaven and live happily in the presence of JC/god forever. Anyway, if you want to increase the revenue of your church/cult, making the laws/restrictions more lax would attract people fairly quickly.
I always say, "Follow the money." JMHO