Why is religion universal?

People have to rationalise phenomena, to explain or understand why something happens.
Many, many things were not, and are not, completely understood. The simplest way was to attribute such things to powers greater than us and that is still done by many today. To shy away from finding out because it was difficult, not immediately apparent or through fear. Fortunately we have progressed and our need to know is, hopefully, greater than our fear of the unknown.