The resignation of Daniel Tarullo, the Federal Reserve’s de facto head of bank regulation, is another step forward for the Trump administration’s plan to ease rules for Wall Street. It will also give the new administration a chance to quickly influence U.S. monetary policy.

Mr. Tarullo’s departure, effective early April, brings the number of vacant seats on the Federal Reserve Board to three out of seven. Donald Trump’s views on monetary policy are unclear. But he is clearly of the view that excessive bank regulation has held...