What is the Most Likely Explanation for UFOs?

Hello, I have done extensive research on the UFO phenomenon and have concluded that there is no doubt that they are real, but what exactly are they? There are claims of many people that they are extraterrestrial vehicles, but how do we then explain why some UFOs tend to exhibit non-material properties or the fact that the occupants of the vehicles range from being alien-looking things to being angelic beings to other mythological-looking things?

I am also confused as to why the government would waste a ton of money on SETI if they actually found aliens. Wouldn't that be counter-productive in many ways? This would point to me that these beings and crafts are multidimensional in some sense. How the hell they even got here: I'm not sure. I find it interesting, however, that depictions of the vimanas in Ancient Indian folklore sound remarkably similar to spaceships.