Someone first came up with the concept of god or supernatural higher entities. Before monotheism were paganism and animalism.
From thereon, many made convoluted additions to such concept, developing the toolkits of social control and grouop identity. From thereon, there are spinoffs, and spinoffs of spinoffs, turning into sectarianism. Old Judaism spawned Islam and Christianity. And each has different sects, Catholics and Protestants, Shia and Sunni and Sufism.
Of beliefs of higher entities with multitudes of rules and protocols, are man-made social rituals that organises groups of people and organises society when adopted at a mass scale.
If such entity is real, it does not care enough to even show itself evidently to the living. Promising that only after death will it all be evident. Who made such promises? The pretenders of prophets who seeked their own greatness?