<Del's post can bring some thinking.
Judaism was the first large scale monotheistic religion, but it was only for the "chosen" ones, not universal. At that time, the Greek and Roman religions were polytheistic which meant gods were fighting each other and no were definitely holding the Truth.
Then, at a time when many suspected the Messiah would come, there came a guy surrounded with alleged abilities, with words and followers who made him well known but also a threat to the the power in place and he was crucified. Some say he came back and more and more worshipers followed his words.
Roman emperors saw in that movement (or sect) a good way to establish authority and Constantine became a Christian, after Diocletian persecuted them. And Christianity started its expansion, also because its God was universal and full of love and mercy, it was unthinkable to be confronted with anyone who'd disagree.
God is Love and Mercy...how can you hate him? And then started the christian persecutions. But it wasn't satisfying, so many interpretations evolved from the original messages (interpretations are human ones, of course). One day, somebody in the Middle east made the remark chrisitianity was not monotheistic: there are 3 deïties: the Father, the Son and the Holy Ghost. However, he said, there can only be one universal source of Love and Mercy: God himself, and thus came Islam, as universal as Christianism but without a "messenger" like Jesus.
Well, why are religions so popular? Because they give a meaning to one's existence?, Because we need answers to what happens after death? Because we always need answers to things we don't understand even when there is no tangible proof?
Well, all I know is I wasn't always there and I won't be there anymore after a while. I'll return back to what I was before my birth and once there, I won't have to worry anymore, it will be the Big Blackout and that's it.
Unacceptable??? But why? Because we are in good health, we have no problems, we have hopes to achieve this or that? I know many very old people who's state of mind about this has changed and accept they might leave this world anytime. The fear of death is largely cultural.
However, what we must far more appreaciate is what our parents and ancestors have given to us: an advanced and curious civilization capable of understanding (or trying to) the Universe and taking its first steps out there.
Last night, I saw the constellations Gemini, Orion, Taurus, Canis Major, Canis Minor, Auriga and 2 intruders, 2 eyes in that huge face, Jupiter on the left and Saturn on the right : it's a fantastic true show, it's forever changing; the lights we see from M42 originated 1,500 years ago from that place , centuries before my birth but it is only now we can see it, just as there is light on its way to here that has left the place long before my birth and will only arrive long after I die.
Where does it place us? Well, nothing much....But we shouldn't worry about this; what's important is to understand our place but not try to correct it by unprooved statements. We can and should improve our human condition but only within the limitations that are affordable to us, limitations that science and technology can alter .

Raoul