What’s a conspiracy theory you actually find believable?

I do believe in extraterrestrial life. I can even go so far as to say that I would not be surprised if aliens knew about us. What I do find hard to imagine is that they have had anything to do with us willingly. If they know about us or are able to come here and research us, I find it hard to believe that they made contact. We would look very primitive compared to them and their capabilities. Perhaps an alien crash landed and several governments are hiding the remains. That would not be surprising, but it still would not tell us very much about the aliens. I doubt we would learn much at all from anything that remained from a crash. It would also go to prove to the aliens that we are not ready for contact.

There has to be someone besides us in the universe. It is too vast and we know too little to be able to guess at what may be out there.