I mentioned this before, but I wanted to revisit it. If you were an alien, or you were some type of intelligent being living your life out in the universe, there would or could be the possibility that your existence becomes threatened when humans finally had the ability to create the atom bomb.
That bomb was tested in New Mexico, and later dropped on Nagasaki and Hiroshima. Perhaps that created a wave of disturbance that stretched into deep space, and life out in the universe was like woah?! WTF was that.
They were a little late, but eventually they did arrive in Roswell, New Mexico two years later in 1947. The mission cost them their lives.
Is this scenario so hard to believe? Isn’t it coincidental?