Colonial and Confederate statues toppled. Looted objects returned by contrite museums. Tainted family names such as Sackler expunged from buildings. A worldwide reckoning with the past crimes of great powers is under way. But is there a glaring omission? A new book, Nazi Billionaires , investigates how Germany’s richest business dynasties made fortunes by aiding and abetting Adolf Hitler’s Third Reich. It also examines how, eight decades later, they still escape close scrutiny and a nation that has done so much to confront its catastrophic past still suffers a very particular blind spot. “What struck me was this is a...