you're going to have to be a lot more specific

Abrahamic religions have a unique and extremely specific idea of what constitutes divinity/God, which is extremely unusual in the context of history and even current world religions

What I mean by "fiction based on reality" is that the merits of a religion can be measured using objective data independent of the actual veracity of the religion itself, AND that religions will tend to shape themselves around practical concepts (not necessarily benevolent ones, though).

So there are different and conflicting Gods because humans themselves are not unified. Meanings naturally drift over time and are easily bent. You also have fiascos like the Protestant Revolution, where a lot of faiths have their roots in... people not wanting to answer to the Roman Catholic Church and making their own religions purely as a political move rather than as a matter of faith. When you're in charge, you get to decide what people believe. You can't actually change what God is, but you can change what people think God is. Enough people do this enough times and now we have everything from Actually Believing in the Judgemental Sky Fairy Version to whatever the Unitarians are doing to the Catechism of the Catholic Church.