In the spring of 2018, President Donald J. Trump signed a law that watered down the landmark regulatory reform act that his predecessor had enacted following the global financial crisis. The changes won a surprising supporter: the liberal former congressman Barney Frank.Mr. Frank was a primary architect of the Wall Street Reform and Consumer Protection Act, better known as Dodd-Frank. But since his retirement in 2013, he had repeatedly voiced support for softening one of the law’s key planks: that any bank with more than $50 billion in assets should face especially intensive federal supervision.The ensuing tweak — lifting the threshold to $250 billion — had big consequences. Among other things, scores of very large banks would escape, at least initially, the Federal Reserve’s annual “stress tests” and enjoy easier financial-safety requirements.One beneficiary of the change was Signature Bank, a New York lender whose board of directors …
