Cardinal Montini of Milan has been considered by some as a potential papal candidate in 1958, but as a non-member of the College of Cardinals was not eligible for selection. Pope John XXIII was chosen instead, seen as something of a non-entity and a safe choice by those who voted for him. He turned out to be the greatest reformer the Papacy had seen in centuries, calling the epochal Vatican Council II that changed the dogma and practices of the Catholic Church more than any single event since the Council of Nicea 1600 years earlier.
John died in office, and Giovani Montini became Pope Paul VI, inheriting the still going on Vatican Council II, which he saw completed and its reforms implemented over the course of his 15 year reign. Paul’s particular focus was restoring relations with the Orthodox churches of Eastern Europe who had split from the Catholic Church centuries earlier, but he excluded no one in his reaching out to all Christians, other faiths and even atheists. He was also the first Pope to visit six continents.