The decisions attested to a president riled up by cable news and unbound. Mr. Trump appeared heedless of his staff, unconcerned about Washington decorum, or the latest stock market dive, and confident of his instincts. He seemed determined to set the agenda himself, even if that agenda looked like a White House in disarray.

Inside the West Wing, aides described an atmosphere of bewildered resignation as they grappled with the all-too-familiar task of predicting and reacting in real time to Mr. Trump’s shifting moods.

Aides said there was no grand strategy to the president’s actions, and that he got up each morning this week not knowing what he would do. Much as he did as a New York businessman at Trump Tower, Mr. Trump watched television, reacted to what he saw on television and then reacted to the reaction.