At the heart of Russian foreign policy sentimentalism is a tendency to view relationships between states as relations between leaders. It is this highly personalized view of the world that helps explain why Mr. Putin, the man who seeks to defeat America, is such an enthusiastic supporter of Donald J. Trump, the “brilliant and talented leader” who promises to make America great again.

Mr. Putin’s predilection for Mr. Trump has nothing to do with the Kremlin’s traditional preference for Republicans. It also can’t be explained by the fact that had Mr. Putin — a physically sound, aging, gun-loving and anti-gay conservative — been an American citizen, he would have fit the profile of a Trump supporter. Nor is it a function of tactical considerations: that the nutty billionaire would divide America and make it look ridiculous.

Rather, Mr. Putin’s puzzling enthusiasm for Mr. Trump is rooted in the fact that they both live in a soap-opera world run by emotions rather than interests. Perhaps Mr. Putin trusts Mr. Trump because the American businessman reminds him of the only true friend the Russian president has had among world leaders, the former Italian prime minister Silvio Berlusconi.