His dramatic decision paved the way for the conclave that elected Pope Francis as his successor. The two popes then lived side-by-side in the Vatican gardens, an unprecedented arrangement that set the stage for future “popes emeritus” to do the same. Benedict stunned the world on Feb. 11, 2013, when he announced, in his typical, soft-spoken Latin, that he no longer had the strength to run the 1.2 billion-strong Catholic Church that he had steered for eight years through scandal and indifference. VATICAN CITY — Pope Emeritus Benedict XVI, the shy German theologian who tried to reawaken Christianity in a...