The explanation is not so difficult. In the opening paragraph of his novel Ravelstein, Saul Bellow writes, "Anyone who wants to govern the country has to entertain it." Clinton has been called many things, but "entertaining" is not one of them. This is not the case with Trump, who is an authentic American character like something out of Mark Twain. All the other candidates except Sanders had the character squeezed out of them when they decided they wanted to be president. Trump's a phony of course (not to mention a racist), but his phoniness is authentic. He's self-made - not in the financial sense, but characterologically.
And what a character! You always want to know what he will say or do next. To be sure, it's not really the president's job to keep the citizenry entertained, although voting on the basis of entertainment value is not entirely irrational, given that entertainment is the main benefit you're likely to get from the US political system. Anyway, not knowing what he'll do next does have its charms, and they go beyond entertainment.
During the nuclear standoff of the 1960s and 1970s, Richard Nixon and Henry Kissinger took advantage of a doctrine out of the branch of economics known as game theory, which holds that sometimes it pays to be - or at least to be perceived to be - crazy. No rational person would ever start a nuclear war. So the one who can get the other side to back down in any future nuclear standoff is the one who convinces the world that he or she is more irrational.
Vladimir Putin has done a pretty good job here, you have to admit. Imagine Putin and any of the American presidential candidates facing each other across the nuclear divide, each threatening to push the button unless their demands are met. Which of the Americans is crazy enough to actually do it?
When Barack Obama proposes something, you know it's been analysed and balanced and weighed against the alternatives, tested in the laboratory and found to be a reasonable solution given the limitations and under the circumstances.
When Trump faces some similar challenge, you don't know what he's going to say or do. And if he says he's going to do something crazy, like get the Mexicans to pay for a wall across their own country to keep themselves out of ours, you can't be sure he won't actually try to do it.
It's clear now that the title of Trump's book The Art of the Deal actually reflects a philosophy of life: Trump believes that everything in life is a negotiation, a deal, and he believes that making deals uses skills that he has and his rivals lack.
This is why he may even have been sincere in his puzzlement about why the media has been so insistent that he should reveal his tax returns. Paying taxes, like so much else in life, is a negotiation - at least at Trump's level. And why would you give your opponent a major document, whether it reveals misbehaviour or not? What is misbehaviour, for that matter? It's all up for negotiation.
People (read: liberals) are afraid of what Trump might do as president. All this silly talk about moving to Canada.
But the thing to really worry about in a Trump presidency is what happens a couple of years from now, when people who have invested their hopes in Trump and his magic tricks discover that he is not the Wizard of Oz but rather the man behind the curtain.