Over the past nine days, as the Trump White House went on the road around the Middle East and Europe, the rest of the world learned first hand what America already knows: this is a presidency unlike any other in history.

Trump left the US under the shadow of a wide-ranging investigation into contacts between his aides and Russia before and after the November presidential election. In his absence from Washington, that shadow has only grown longer and darker.

The latest in the string of daily developments was a report on Friday night that Jared Kushner asked the Russians to set up a secret channel of communication with the Trump transition team, bypassing US diplomatic and intelligence channels. It was a stunning revelation, given that Kushner is not just the president’s son-in-law but his closest foreign policy adviser. When Trump met Israeli prime minster Benjamin Netanyahu, for example, Kushner was in the room but national security adviser HR McMaster was left outside.

The White House’s primary aim for the tour was to achieve Barack Obama’s touchstone goal: “Don’t do stupid shit.” For a few days, that seemed to work. The Saudi and Israeli legs of the trip were tightly controlled, Trump stuck to his scripted remarks, and the president made his keynote counter-terrorism speech in Riyadh in a deliberate and determined manner.

It was only when Air Force One reached Brussels that the caravan began to lose its way. That was perhaps inevitable for both policy and personal reasons. With King Salman and Netanyahu, there was a shared list of priorities and talking points: a view that Iran was a primary enemy, the desirability of huge US arms contracts, denunciations of terrorism. Trump was the centre of attention, literally treated like royalty and assured the things he did and said were “historic”.

In Europe, Trump had to play a different role: a senior member of a group seeking to act in concert and by consensus. But Trump does not do collegial, a fact that was grasped before in Europe but is now viscerally understood after the president shoved the Montenegrin prime minister out of the way to get front and centre of a Nato leaders’ photo-op.

These are the ways of a man without curiosity. He does not read books, and listens fitfully and reluctantly to others. He is reportedly fed up with McMaster because he goes on for too long about world affairs. The briefing papers McMaster’s team drew up before this trip had to be condensed to a few bullet points on a single page for each issue, and even then Trump grew bored of reviewing them before departure, and groused about how long the whole excursion would take.

The lack of preparation began to show when he reached Brussels. At Nato, his prepared remarks at a 9/11 monument were largely a retread of his campaign speech about the alliance, which in turn was constructed around a misunderstanding of how it works. He accused the US allies gathered alongside him, in the shadow of a shattered fragment of the World Trade Center, of being deadbeats who had not paid their club dues.

In terms of the common expenses of running Nato headquarters and infrastructure, this was simply not true. When it comes to the goal of Nato members spending 2% of their GDP on defense, the deadline is 2024, and the European allies have been increasing their expenditure since the Russian annexation of Crimea. And they have been contributing in other ways, including by way of blood and human lives in Afghanistan.

Trump’s denunciation of the Germans at a European Union meeting for being “bad, very bad,” because of the large number of German brand cars sold in the US, showed his comprehension of the global auto trade was just as shaky. The vast majority of German cars sold in the US are made there by American workers. For example, the BMW plant in South Carolina is the company’s largest anywhere in the world. It is also the biggest exporter of cars from the US.

Trump lack of grasp of the realities of geopolitical alliances and global trade is a reminder that he came to office at the age of 70, having spent his entire adult life in a single business, real estate – a business he inherited, and which was built on bluster, gaming the legal system and forming partnerships of convenience with equally ruthless operators.

By the time they reach three score and ten, people generally do not change their ways, and Trump’s grand tour has served a reminder of that. He has not suddenly transcended the world of real estate to become a statesman. He is just going about the work of a president as if it is an extension of his real estate business.

To the Belgian prime minister, he explained his antipathy to the EU because of obstacles he met while trying to send up golf courses in Europe. The same failure to adapt is likely to be a big factor in the Trump family’s troubles with Russia. Both the president and Kushner have grown up going from one deal to another, looking for finance wherever it came from, in secret when necessary.

They evidently assumed affairs of state could be conducted in the same way. What is yet to be proven, but which should become clearer once they return to the US to face further investigation, is whether they will be proved wrong in that assumption, or whether the United States will be suborned and remade in the image of the Trump Organization.