He seems to combine the “madman” theory with “good cop, bad cop” to produce a “crazy leader, sensible leader” tactic. It’s probably a very effective strategy, if all you’re interested in, is optimising the short-term, very narrow, very selfish interests of a part of the US population. It’s a strategy I’d like to try in a board game.
While I'm hope to be wrong and corrected about this, the impression I get is that this is exactly what's already happening. Except it's the 'bad guys' doing what they feel needs to be done.
Take Mexico, for example. Making derogatory remarks about a whole country and its people makes it almost impossible for any politician of that country to negotiate without risking to loose a substantial amount of voters. It's a real diplomatic problem, which is aggravated by the fact that many countries are still trying to figure out whom they can reach in the US diplomatic chain in order to get any reliable reply.
The world is not a board game.