But as you pointed out, he hasn't told us anything about what he does or doesn't know. So on one hand, we have no evidence that he knew about health care or global politics. On the other hand, we have circumstantial evidence that he does not. Including the whole Scotland gaffe about Brexit. What conclusion should I draw?
The opposite is the case. We have no evidence that he (and his team) know nothing about healthcare or global politics. All we know about healthcare is that he failed to simultaneously manage the expectation of the more extreme Republicans and the Democrats (he needed support of one or the other, he bet on the latter, this failed. A mistake I'm sure he'll learn not to repeat). The Scotland gaffe was a lapse in judgement, but he was merely parroting the British government who insists over and over that "the British people have spoken", despite many issues with that claim.
I have little doubt that his team knows a great deal of things and are far more competent than he is. But we're not talking about them, we're talking about him.
As for Healthcare, this is false. He didn't make or even suggest the bill. It was purely Paul Ryan's plan. Trump's idea, as far as we know, was "Give everyone healthcare and make it cheap". That is literally his entire plan to the best of our knowledge. He tried to sell it but he hasn't shown any indication that he had any hand in it's production or language.
A lapse in judgement? No, it was simply him getting information from a poor source. Much like his comment about Sweden because he saw a segment on Fox news that turned out to be of questionable integrity anyway.
Meanwhile, we have ample evidence to the contrary (huge electoral successes, nationwide and international praise after Syria bombing, Democrats left with no choice but to oppose any legislative progress, which in turn will leave them with even less power over time). Trump's successes, as crude, brutish and unfavourable as they may look, are not leaving us anytime soon.
Electoral success is irrelevant to knowledge and you know it. The US elections are a popularity contest, nothing more. He won by the electoral collage, not the popular vote, AND he won by appealing to voters with simple language and simple solutions to complex problems. Solutions that amounted to "I'll do what you want without a problem."
The Syrian bombing was done in reaction to an emotional video, not policy or strategic planning.
And the Democrats are literally doing what the Republicans did for Obama. It worked for them, so why not for the Dems? Heck, it seems to be working for them too. They forced congress to change the rules for a supreme court nomination, paving the way for democrats to use that same rule in the future. They helped stop the Republican Health care plan from being passed (though not the main reason).
Trump is a salesman. He knows how to sell a product. Unfortunately, as president, he has to both produce AND sell a product. And when it comes time to make good on what he promises, he not only fails to do so, but shows he didn't even understand what he was trying to sell.