Just three years ago, Chinese President Xi Jinping skillfully soothed European sensibilities at the annual gathering of global elites in Davos, Switzerland, as he praised the virtues of multilateralism, free trade and fighting climate change.

To many Europeans, China’s authoritarian leader briefly seemed a more appealing partner than President Donald Trump, who has since withdrawn the U.S. from the Paris climate treaty, disparaged the European Union and questioned the value of NATO. Mr. Xi’s ambitious Belt and Road project...