the article does partly have to do with appealing to new voting coalitions that are a popular discussion topic on this site, a taste, with my highlighting:

During the past decade, Mercer, who is seventy, has funded an array of political projects that helped pave the way for Trump’s rise. Among these efforts was public-opinion research, conducted by Caddell, showing that political conditions in America were increasingly ripe for an outsider candidate to take the White House. Caddell told me that Mercer “is a libertarian—he despises the Republican establishment,” and added, “He thinks that the leaders are corrupt crooks, and that they’ve ruined the country.”

Trump greeted Caddell warmly in North Charleston, and after giving a speech he conferred privately with him, in an area reserved for V.I.P.s and for White House officials, including Stephen Bannon, the President’s top strategist, and Jared Kushner, Trump’s son-in-law. Caddell is well known to this inner circle. He first met Trump in the eighties. (“People said he was just a clown,” Caddell said. “But I’ve learned that you should always pay attention to successful ‘clowns.’ ”) Caddell shared the research he did for Mercer with Trump and others in the campaign, including Bannon, with whom he has partnered on numerous projects.

The White House declined to divulge what Trump and Caddell discussed in North Charleston, as did Caddell. But that afternoon Trump issued perhaps the most incendiary statement of his Presidency: a tweet calling the news media “the enemy of the American people.”

The proclamation alarmed liberals and conservatives alike. William McRaven, the retired Navy admiral who commanded the 2011 raid that killed Osama bin Laden, called Trump’s statement a “threat to democracy.” The President is known for tweeting impulsively, but in this case his words weren’t spontaneous: they clearly echoed the thinking of Caddell, Bannon, and Mercer.

and

[....] A brilliant computer scientist, he helped transform the financial industry through the innovative use of trading algorithms. [....] he is painfully awkward socially, and rarely speaks [....]

In 2010, when the Wall Street Journal wrote about Mercer assuming a top role at Renaissance, he issued a terse statement: “I’m happy going through my life without saying anything to anybody.” According to the paper, he once told a colleague that he preferred the company of cats to humans.

Several people who have worked with Mercer believe that, despite his oddities, he has had surprising success in aligning the Republican Party, and consequently America, with his personal beliefs, and is now uniquely positioned to exert influence over the Trump Administration [....] After the Journal story appeared, Magerman, who has worked at Renaissance for twenty years, was suspended for thirty days. Undaunted, he published an op-ed in the Philadelphia Inquirer, accusing Mercer of “effectively buying shares in the candidate.” He warned, “Robert Mercer now owns a sizeable share of the United States Presidency.” [....]