The resurrection of Donald J. Trump as president reflects a long-gathering revolt against the established order, driven by a disorienting world of social fracture, shared truth, and hope collapse. The victory of Mr. Trump, dismissive of climate change and supportive of authoritarian leaders like Vladimir V. Putin, has deepened divisions and posed threats to global stability. With wars raging in Europe and the Middle East, the rise of nationalist movements, and the potential splintering of the European Union, the international system faces a dangerous mix of turbulence and a turbulent personality in Mr. Trump. His victory represents a wider phenomenon of seeking simple answers in a complex world.