God does. That’s the point. The Catholic belief, which is written into the very doctrine and dogma of the religion, is that God is guiding the process and that God chooses the Pope. The whole religion is based on the idea that Jesus took the wheel and handed it to Peter afterwards who then handed it to the next person. Papal infallibility, as a concept, is the promise that the leadership of the Catholic Church is free from human error so, yes, according to their own beliefs, they are explicitly immune from that.