I'm more in the former camp that Mr. Trump is a buffoon as you described early in the essay. I don't see a mastermind at work. He is appealing to his base, and so far, that seems to have worked out for him, politically speaking. That is what is triggering his reptile brain.
Maybe his base wants a civil war. If so, Mr. Trump would be capable of delivering one. There's going to a lot of chaos in the few weeks leading to November 3.
If we don't want this scenario to happen again, we need a different electoral system where the likes of Mr. Trump (and Ms. Clinton) won't rise too high.
Tiered Democratic Governance.