I read presidential biographies for fun, and I can watch basketball for hours. So when Jared Diamond published a book about how much one leader can change history, using basketball coaches as a test case, it felt like it was written for me. Diamond is the UCLA professor who won a Pulitzer for Guns, Germs, and Steel: The Fates of Human Societies in 1998. His new book, Prophets, Profits, Coaches, and Kings: (When) Do Leaders Matter?, asks whether the 20th century would have looked different without Adolf Hitler, Winston Churchill, or Mao Zedong. Diamond has carried that question for decades. I asked him if the war and the Holocaust would have happened the same way without Hitler. He thinks they wouldn’t have, though the historian A.J.P. Taylor studied the same facts and decided Hitler was an ordinary German politician. In our conversation, we ran through some of the biggest figures of the last century, from Churchill and Joseph Stalin to Mao and Margaret Thatcher. Lee Kuan Yew ran Singapore as a benevolent dictator and then stepped down, and Thatcher divided Britain in a way that changed everything. Diamond admits that biographies can’t prove any of this, so he also compares what happens when a leader dies in office with what happens when the leader stays on, a method he says now covers more than 200 cases. We ended with sports, which Diamond sees as the best lab for studying leaders—every team plays the same schedule under the same rules, every result is public, and a coach’s record can be compared with the one before it, which is hard to say of a CEO. He also had a verdict on his own university’s basketball team, which has gone through coach after coach since John Wooden: UCLA should have read his book.