Religion is a powerful concept; it is certainly more than 'a particular system of faith and worship' as suggested by merriam-webster.
People often confuse Religion with God. God is the supernatural; Religion is supposedly the path to reach the supernatural.
If we understand the difference between God and Religion, we realize that God is something man made and so is religion and neither need to have been created by the same person. Hence these 2 could have had entirely separate principles at the origin. Logic dictates that loving and forgiving fellow human beings is higher than any calling. However, the purpose of religion seems to be more dictating about God and not human beings.
Because of multiple religions, there are multiple Gods. The central idea of the person who created/invented GOD couldn’t have been to create a supernatural per species/caste/geography or culture. God was supposed to be the supernatural for entire universe (yes that includes the aliens too).
But the person, who created religion, certainly had a different idea. This person, let’s call him ‘Rel’ or that group of people (1 for each religion) wanted to be God for their own community. So Rel was not happy with the way God took all the credit for everything and left powerless.
Now to support his theory, he used God to dictate the ‘terms and conditions’ of religion. To add authenticity, he had to surround it with stories, theories, books, incidents and witnesses. If all of above mentioned can be created today with a good fat checkbook for the stupidest of the products ever sold in market, I think it would be fairly easy to create one that time for a smart guy.
But all of that seemed to fail when people of equal or more intellect came along and challenged his concepts. So he added some exclusivity terms to his religion. This helped him create a distribution network with good balance between R and A. Responsibilities and Authorities. So obviously he made sure people got a good balance of these too to attract them to his religion.
Let’s make God exclusive to people who follow religion. This was the best way to establish exclusivity and promote the product using curiosity and fear at the same time.
As time passed, generations of Rel came and kept using the same concept to make fool out of common people.
Now some people say that if religion was not there, people would have lost faith. That’s a good point, but you don’t need to have faith in God. It is something that Religion has told us is mandatory, the guy who created God did not tell us so.