According to his theory other cultures/races/civilizations …

According to his theory other cultures/races/civilizations are hiding in the deep, mainly because our world is being hit by cataclysms once in a while.
And the best way to survive it is to hide in the deep.
The main reason I find it plausible is that mainstreammedia is propagating space, interplanetary travel and other stuff which concentrates on the above.
But there is not much about the underground.
It would also make much more sense to put bases on the ocean floor, into the water or underground first, before colonizing mars.
If mainstreammedia concentrates so much on the above you whould look the other way.
And he thinks that humanity has something like a "benefactor" in this construct or on the outside, since without one we would have been enslaved already.