David Kass, a finance professor at the University of Maryland, is a longtime attendee of Berkshire Hathaway’s annual shareholder meeting in Omaha, Neb.—an event so popular it has earned the nickname “Woodstock of Capitalism.” In past years, Kass saw lines forming around the block as early as 6 a.m., along with overflow rooms and packed exhibition halls. This year’s gathering, held last weekend and the first led by Berkshire’s new CEO Greg Abel, …