On Thursday, President Trump fired Kristi Noem, his secretary of homeland security, whose agency is at the center of his second-term agenda. Hamed Aleaziz, who covers the department, explains how Ms. Noem ended up losing the president’s trust. Guest: Hamed Aleaziz, who covers the Department of Homeland Security and immigration policy in the United States for The New York Times. Background reading: Bulletproof vests and Rolex watches: the rise and fall of Kristi Noem. Mr. Trump said he would replace Ms. Noem with an Oklahoma senator, Markwayne Mullin. Photo: Nicole Hest...