It should be pretty obvious that all religion is man made.
All one has to do is put themselves back in the time of the beginnings of any religion to see how it truly evolved. You can also easily see how different religions sprang up in different places.
If God can do all... created the whole world in 7 days... well 6 he rested one. He or she or it certainly coulda/woulda came down everywhere to get that "understand me" ball rolling. But of course that didn't happen because it's all man made up from wherever the different groups or tribes were.
Various tribes all over the world were mystified by most anything. There was virtually no science to rely on and things needed to be explained. Plus every tribe wanted to hold it's power and most wanted to enforce their power onto others (kinda like the Religious Right today
).
There is no greater tool for trying to do this than to be able to say... God is on OUR side. Every side says it. It's the proverbial trump card.
Add to that all the millions of scientific events that we take totally for granted today because through science, medicine, research, discovery and education we know it's not magic... our the Gods... or the cookie monster and you can understand why normal events like floods & volcano's, tornado's, plagues and everything else just fit into "stories".
An exceptionally smart man or kind man or strong man could easily be seen as someone from GOD! And what couldn't be covered by that they put a deity up in the clouds (and one in a fire pit if you were naughty) that could not be dis-proven.
Couldn't be proven either but that didn't matter. It was THEIR GOD THE ALMIGHTY!
Religion was nothing more than a way to try and keep people in line at times & places before government and as a competing authority during times of government.
Nothing more.