This is one of those Trumpisms that derive from his profound ignorance, because he beat up some nerd to do literally every homework assignment in his life. A famous one is "Bigly," because he didn't understand when he first heard it that they were saying "Big League."

For a long time, I wondered what "very stable genius" meant, and it finally dawned on me. He must have heard someone described as a "veritable genius," and he decided to apply it to himself, and it garbled out as "very stable genius."

or of a deliberate strategy to destabilize the current world order for some reason.

even if trump himself may be 'dumb', he is working with the other ghouls to try and stop the empire from collapsing at any cost. (it will anyway)