Five years after Hillary Clinton titled her latest memoir, “What Happened,” the revolution that hit American politics in 2016 remains little understood. When the former secretary of state joined me on air to discuss her book in 2017, she’d worked out in her own mind what drove the most improbable upset in modern political history.

Clinton told me. “I understand the resentment. I understand the very strong feelings that a lot of people in our country have about everything from the economy to race to immigration to national defense.”

But the cataclysm of 2016 is more complicated than that. Even now, do any of us who live inside the Beltway bubble or who swim in the waters of “elites” really understand?

Now comes an explanation from Walter Russell Mead, a scholar of U.S. foreign policy, national politics and national security as well as a past professor at Yale, who gets very close to the answer. I have no idea how Mead votes. To me, he’s always been a respected voice whose wide-ranging interests and scholarly credentials are not in question. He’s not a political analyst in the way the term is used today.

So it was a surprise that Mead used the final chapter of his latest book, “The Arc of a Covenant: The United States, Israel, and the Fate of the Jewish People,” to reexamine what happened in 2016.

Mead’s whole book deserves an in-depth read, but for those in the political analysis business, the final pages are worth the cover price. “Getting to grips with the Trump presidency is a trying task,” concedes Mead. “Trump was such a unique and controversial figure that both his achievements and his failures defy conventional analysis.”

“Yet with all his many shortcomings,” Mead continues, Trump “understood some important truths about international politics and the state of the world that eluded his establishment critics.

“To millions of Americans, [Trump] was like the little boy who dared to cry out that the emperor had no clothes — that the American elite had lost its way and had no answers for the problems of the United States, much less for those of the world beyond our frontiers.”

The folks caught most unaware of the undertow in 2015 and 2016? Republicans like me, categorized by Mead as Sun Belt Republicans, not so because of where we lived but because of our broad commitment to “optimism, laissez-faire conservatism, free trade, and a vigorous promotion of American values abroad and at home.”

We were blindsided by Trump, both his march through the primaries and his eventual upset in November 2016. The “Republican establishment, both intellectual and political, were the ones to suffer defenestration as Trump stole the Republican Party out from under them in 2016,” Mead observes.

Trump tallied 63 million votes in 2016, and he collected even more — 74 million — four years later. He lost the popular vote to Clinton by almost 3 million and to President Biden by 7 million.

Why were voters pulling the lever for Trump? They expressed their disapproval of who had come to govern American life, left, right and center, and what those “elites” had set as their priorities.

“If the mid-century model of an American economy built on the growing success and stability of a middle class no longer worked, what kind of society was the United States? … And if the United States could no longer see itself as a providential nation with a global mission,” Mead writes, “what did it mean to be an American?”

Similar forces are at work in other Western countries. Democratic electorates across the globe have been voting since World War II, Mead explains, to govern themselves via people like themselves who share their values. They have voted again and again against elites, especially elites embodying different morals and world views, he said. Even Ukraine’s struggle against Russia can best be understood in this context of “self-rule first,” Mead told me Monday.

Finally, he writes, a broad cross section of voters “wanted less and less to do with conventional Republican foreign policy. They still scorned Democratic talk about multilateralism and international institutions, but they no longer saw establishment Republicans as trustworthy opponents of the Democratic agenda at home or abroad.

“By 2016, millions of GOP voters were ready to strike out in a new direction. Donald Trump was in the right place at the right time.”

Read Mead. He has provided the balanced, persuasive short course on all that we need to understand.