All the major religions in the world have the same God, the one and only Universal Creator of all that is. Creation may have occurred all at once or through an evolutionary path. The Creator God may be unknowable, except through a deep meditative process; or knowable, perhaps through revelation. Asking what was there before Creation, or about the origin of God, are meaningless questions. (Ask the cat which looks behind a free-standing mirror for that other cat.)
Most of us need a saviour offering succour, primarily in terms of survival in our normally harsh environments. Others may have lesser needs, but which can loom large in their lives, depending on how insecure or greedy they are. Wants may be greater than need.
A significantly powerful personal need, but which can (in an exaggerated state) threaten the very existence of other humans who are also believers in God, is the need to believe that one is on the only path to God; or that one’s path to the Celestial Abode of the Heavenly Father is the more efficient one. This Abode may offer angels, or dancing girls, or advanced spirits, or ever-lasting peace. (Or perhaps a wondrous mansion filled with gee-gaws of great value, and serviced by valets galore.)
How does such a strange need of exclusivity or superiority arise? Surely through the priesthoods. Why would priesthoods need to compete with one another? The exercise of power, or a collective ego-gratification?
Religious belief systems arose in widely dispersed regions of the world over a long period of time. Each could not have known about other belief systems unless traders from afar displayed their foreign faiths. See what happened when Hindu and (later) Buddhist traders influenced the cultures of South East Asia and the islands of the adjoining archipelago now known as the Indonesian. So many individuals there have names and even facial features which reflect this cultural infusion.
Of course, marauding armies would also have imposed a new religion here and there. Or, a ruler, by accepting a new religion, had all his people follow him.
Priesthoods would also tend to protect their reign when they control the path to eternity. As evidenced in Egypt, when Aten replaced Amon temporarily, it was allegedly the prevailing priesthood which recovered the status quo. Was this also the earliest evidence of a closed trade union?
But then, why did Christianity, which offers a loving universal god in place of a fearsome desert god, set out (through colonialism) to convert peaceful followers of the forest religions of Asia? What drove Islam, the successor to Christianity, to use the cutting edge of weaponry to convert all and sundry? Do not these religions have a record of destroying the followers of other faiths, and sects of their own religions, here and there? In my experience, these are the only 2 religions whose followers talk a great deal about their faith, whereas the others simply live their religion.
It is surely undeniable that the 3 major desert religions have been, and are, the predominant warring nations of the globe. Humans will, of course, attack one another for material gain. Our simian genetic heritage is probably responsible. But what gain is there in collecting souls? Why not take the coveted materials, and leave beliefs alone? More efficient control of the ‘other,’ using priests?
In any event, the diversity of beliefs reflects merely the diversity in approaches to the Divine. The paths do vary, thanks to differences in man-made theology and dogma – all arbitrary, and replaceable. On what basis would a priesthood claim superiority or priority?
Would not the wanton destruction of fellow-humans and their societies in the name of one’s religion affect one’s chances of finding peace in the Hereafter? Or, do the guilty deny the existence of a meaningful Afterlife?
Why not live in faith on Earth, and allow others to live with their respective faiths too? In the Afterlife (Hereafter or Heaven) all souls will surely be equal as non-entities!