Confidence Man: The Making of Donald Trump and the Breaking of America by Maggie Haberman:
He had been in a sour mood from the time he boarded Air Force One at Andrews Air Force Base. Over the Atlantic, he had erupted by phone at British prime minister Theresa May with a litany of perceived grievances after she tried to play to his vanity by congratulating him on his party’s midterm successes. After arriving in Europe, Trump praised Adolf Hitler, saying that he had accomplished some good things. Some who were told of the remark in real time suspected—and perhaps hoped—that it was intended purely to provoke Kelly. Even when Trump didn’t intend to tweak Kelly, he managed to offend him: at one point during Kelly’s tenure, Trump questioned in Kelly’s presence why people would choose to go into the military. At that moment, he and Kelly were standing together at the Arlington National Cemetery gravesite where the retired general’s son was buried.
Kelly and Dunford ended up heading to Belleau alone, as Trump remained in his Paris hotel room. A few explanations went around for the last-minute cancellation. The weather was bad, and traveling by car instead of helicopter would take too long or force the closure of too many Paris roads. However, Kelly deputy Zach Fuentes alerted other officials to the decision not to travel about fifteen minutes before the Secret Service made its determination about the safety of flying. Media coverage of Trump traveling all the way to France only to skip the ceremony honoring American war dead was predictably critical (and included several accounts from staff saying anonymously that Fuentes had been responsible). When he saw how his trip was being covered, Trump screamed at staff, complaining that the decision not to attend had been made for him and that he could have gone after all. It was reported much later, by The Atlantic’s Jeffrey Goldberg, based on several sources, that Trump had derided the war dead and told Kelly that he did not want his hair to get wet in the rain.