That's easy -technology. UFO phenomenon and all paranormal phenomenon follow right along with technology and current socially accepted view of reality.

The Scopes Monkey Trial was approximately one generation in public education prior to widespread belief in UFOs and ETs replacing "evil spirits", "witches on brooms", elves, fairies, etc.

The UFOs do things that seem to defy the laws of physics because they aren't what they seem to be. They are inter-dimensional beings who have been referred to in the past as elves, fairies, djinn, angels, demons, trickster spirits, etc.

So why do they do the crazy things they do? Who knows? How can you rationalize the actions of an entirely different entity, let alone one not restricted to your own limited dimensional existence? Perhaps we're their interactive television set or the equivalent of a child's toy to them? Maybe it really is part of a big universal war between good and evil? Maybe not?

One things for certain. Actual physical you-and-me physical beings living in our restricted dimensions, they are not! The evidence clearly indicates such, not to mention the laws of physics and the problems associated with interstellar travel as well as the logical question of "why just put on light shows and abduct people for 70 years after traveling all this distance?"