Trump clearly has quite a few problems as president, but for a quick summary of why his ignorance is such a hindrance to his success, you could do worse than pointing to these two paragraphs.When Trump says, “But it’s not what you would think,” what he means, of course, is that the details aren’t what he thought. The president believed the dynamic was simple – he’d just tell China to control North Korea, as if the latter is reflexively subservient to the former – but he “realized” after talking to Xi that it’s not as “easy” as he’d assumed.To be sure, I’m delighted that Trump has learned something important, but what the president may not realize is how embarrassing his acknowledgement is. He’s effectively saying that he made a series of assumptions about two nuclear-powered countries; he campaigned on those assumptions for a year and a half; and after three months in the Oval Office, he’s just now realizing – following a private tutorial from the president of China – that his overly simplistic understanding wasn’t exactly accurate.“After listening for 10 minutes, I realized it’s not so easy” is perhaps the quintessential Donald Trump sentence.The same WSJ article added that Trump told his Chinese counterpart this week that Xi “should let North Korean leader Kim Jong Un know the U.S. doesn’t just have aircraft carriers, but also nuclear submarines.”Does Trump not realize that the world has known for decades about the nuclear triad? Or is this something that the president himself just recently learned?Trump also told the Journal, “You cannot allow a country like that to have … nuclear weapons.” Really? Because they already have nuclear weapons.There’s also the broader context to consider. The Washington Post’s Dana Milbank recently wrote , “Trump’s discoveries of seemingly obvious things raise two possibilities: 1) He thinks people are awfully stupid, or 2) he is discovering for himself things the rest of us already knew. Which is true? Nobody knows.”Perhaps not, but I’m leaning towards the latter. Trump didn’t realize that the Assad regime was responsible for horrific atrocities. He didn’t realize reforming the nation’s health care system would be “ complicated .” He “ didn’t realize ” the nuances of how Congress works. He thought private-sector deal-making was effectively the same as reaching governmental agreements, and was surprised to discover otherwise.There’s a learning curve for being president. For an amateur unfamiliar with public service and the details of current events, the curve is evidently steep.