President Trump’s personal assistant was fired because of his high-rolling online gambling, betting tens of thousands of dollars online at a time, according to a report. John McEntee, who was unceremoniously booted from the White House this week, opened himself up to outside influence by frequently betting large sums of money online, two people familiar with the matter told the Washington Post. McEntee’s gambling was likely not illegal, but there was concern among White House personnel that he could pose a security risk by being vulnerable to blackmail. A background investigation found that McEntee’s gambling habits made him unsuitable for…