Reverend Billy Graham was called by God to evangelize. He was not called to convert non-believers to any particular sect or denomination. His mission was to spread the gospel. Sin destroys the soul. Repentance from sin, acceptance of Jesus Christ as Lord and Savior, and love of God and neighbor leads to eternal life. That’s the essence of the gospel. Everything else enhances one’s relationship with Jesus Christ.
Billy Graham could not have fulfilled his mission as a Roman Catholic. The Catholic Church is too autocratic. It’s bound by rules and prohibitions. It has much to offer, but can be a huge stumbling block to those not from a Catholic background. Catholicism is a religion and culture. The culture can be daunting and off putting to an unbeliever. I’m a convert. It’s taken many years for me to become comfortable with Catholic practices and beliefs, yet I still have difficulty bridging the divide. There are parts of my faith which will always be Protestant.
Billy Graham could not have simply preached the gospel as a Roman Catholic. He would have been required to involve bishops, priests, and the Vatican. It would have included the Mass. In the Pre-Vatican II era that would have required a familiarity with Latin and a style of worship completely alien to someone from a non-Catholic cultural background. As a lay person, his freedom would have been sharply curtailed. He served in the way God desired from his background and millions came to an understanding of Jesus as Lord and Savior. Peace!