Believing in God or UFOs is everyone's business. But here's what I'll say:
I have two opinions about the origin of UFOs. The first is that it's another civilization that is far more advanced than us. They are studying Earth and sometimes take people for detailed study. Why don't they make contact? If they make contact with us and tell us about themselves and their technology, we, as a lower species, will ask them for various technologies, and we won't pass the "evolutionary course." The second opinion is that UFOs are us. What if, in the future, our descendants managed to create a time machine, and the unidentified objects are that machine? Then it becomes clear why they don't make contact...