Now that investment banker Steven Mnuchin has been installed as the Treasury secretary, work can begin on finding a solution to Fannie Mae and Freddie Mac, the giant government guarantors that serve as the linchpin to housing and mortgage markets. For the most part, senior mortgage officials who have been in the business for a decade or more applauded President Trump’s choice of Mnuchin, pointing to his days as the head of MBS trading at Goldman Sachs & Co. “At the very least, this is...