is religion a creation of men?
Nice question! I guess my answer depends on which definition of religion you are referring to. If you mean simply the practice of worshipping a deity, then I would say perhaps not, since I believe the angels worshipped God before man was created. The Bible shows the worship in the 2nd generation of men, with Cain and Abel bringing offerings to God, but that story doesn’t explain where the practice originated, if this was the first occurence, or if it was initiated by man or instructed by God, who still seemed to be in pretty frequent direct communication with men at that time. I am of the opinion that God probably instructed it, since he is a fair God, and it seems unfair to pronounce judgement on Cain for his offering, unless it violated a commandment that Cain was surely aware of.
Now, if you are referring to all of the various sects and cults we see in the world, I think that yes, these are inventions of man, or perhaps more accurately inventions of men inspired by the devil. From my reading of the Bible and study of history and pagan religions, I’ve come to conclusion that Satan and his fallen followers had a hand in shaping these endeavors of man from the beginning, though I think Nimrod was probably the ultimate progenitor amongst men of all of these various cultish belief systems.