I didn't mention one of the theories in this video, which is that all of the aliens are hiding from each other because there is some terrible insidious force in the universe that punishes anyone who is loud. This doesn't really seem likely to me because, look, malevolence is actually pretty rare in nature. Much more common is "I need that, you're using it, I don't care about you, so die" not "I am going to spend a bunch of resources SPECIFICALLY TO COME AND GET YOU." I also kind mis-stated the "Great Filter" hypothesis, because the filter could either be before or after the point where humans currently are, so it's kinda wrapped up in both the first and the second bits.