President Trump’s first year in office was characterized by little movement on some of his signature issues, matched by a great commotion within the ranks of the administration. But so it had to be. He had campaigned as an outsider, and for once that was not a lifelong politician’s conceit. Mr. Trump had no experience in government. He had few friends or allies with such experience to draw upon when he entered office. Even the campaign professionals and aspiring nationalist policy thinkers he drew to his campaign in 2016 were recent acquaintances. That the new administration’s first 15 months should be marked by rapid cycling through press secretaries and National Security Council staff and other advisers high and low is not surprising.

The departures of Rex Tillerson and H. R. McMaster, in particular, do not indicate a sudden swerve in policy: Mr. Tillerson a was a gamble from the beginning, a secretary of state with as little political experience as the president and no very tight ties to him. Mr. Tillerson’s tenure at the State Department has been considered a success by no one. His exit was a matter of time.

General McMaster likewise has never developed a rapport with the president, who chose him as national security adviser only after Michael Flynn was forced to resign and Mr. Trump’s second choice, Robert Harward, a retired vice admiral, declined the role. General McMaster was given a fair chance and allowed to remove from the National Security Council political holdovers from General Flynn’s brief tenure. But his support for the Iran deal has been at odds with the president’s commitment to ending or drastically renegotiating it. The president is determined on his course, and he understandably wants a national security adviser who shares his priorities.

Were he not being replaced by the president, General McMaster would soon have found himself facing the same choice that Gary Cohn had to confront once Mr. Trump followed through on his promises of economic nationalism: to resign or implement a policy with which he firmly disagreed. Advisers are there to offer the president a menu of options, including those he might not find to his taste. Once the president has made up his mind, however, the responsibility of his aides is to see that his orders are carried out effectively. Policy differences have a proper place in an administration, but only before a decision is made.

There always has to be some trial and error involved in building an effective cabinet and White House team, and in Mr. Trump’s case, coming from as far outside the policy world as he did, there was sure to be more turnover than in most administrations, as the president got a feel for personalities and policies. Has a year’s experience now shown Mr. Trump who his real allies and most suitable colleagues are?

That’s one theory for Mr. Pompeo’s proposed elevation to secretary of state. And while Mr. Bolton and Mr. Kudlow have not served in the administration before, they have built strong relationships with the president. Then again, so did Steve Bannon, who proved not to be as close or indispensable to Mr. Trump as an avalanche of media coverage had made him seem. The man purported to be the power behind the throne didn’t last a full eight months in this White House.

The next wave of national-security and economic advisers is not assured of lasting any longer. This is another reason fears of Mr. Trump’s latest staff replacements are misplaced. An old joke attributed to Groucho Marx has a politician declaring: “These are my principles. If you don’t like them, I have others.” The same can be said about President Trump’s personnel — if you don’t like them, he has others.

The new personnel will not make the administration a monolith. Like those who came before them, they will find that the real key to policy lies not with them but with a single unchanging executive branch employee: Donald J. Trump. His great virtue is that he cannot be molded by his advisers; he resists all tutelage. He was elected because the people who do the molding in our politics have for too long led our country down a path of destruction, under Republicans and Democrats alike. The advice they give, sound in theory, is terrible in practice. One service President Trump has performed that even many of his detractors should applaud is to demolish the mystique of the policy elite. He can govern, and we can live, without them.