“Sometimes, you think, you’re the president now, why do you care about that person or insult?” one transition aide said. “No one is really paying attention until he tweets about it. And then you have a whole day of controversy.”…

There is also some strategy to it. He can often dominate news cycles when others criticizing him, knowing his supporters will often take his word and see him in a position of strength. Wayne Barrett, a Trump biographer, said “there’s some genius to it” and that his “very planned” gestures send a message to others who might attack him.

People who know Trump say he often becomes obsessed with grudges, particularly if someone questions his credibility or the legitimacy of his victory or personal characteristics. He stews over insults, sometimes mentioning them days later.

But he can also prove conciliatory, which will keep foreign leaders and others on their toes, Fleischer says. Critics are scared he will change his tune on international affairs based on emotions.