Why The Pope?
Jesus is the Wisdom of God in Person who became man to teach us the full truth and show us the only way to be fully alive with God for ever. He said "I am The Way, The Truth and The Life". He didn't just preach in Palestine for three years then go back to heaven and leave us to try to work out what he meant or what he might teach us today. He gave his Apostles his own authority to teach the Word of God and govern the Church.
He said "whoever listens to you listens to me" (Luke 10,6) and "whatever you bind on earth will be considered bound in heaven" (Matthew 18,18). He also knew there would be questions and quarrels among his disciples, so he chose Simon to be the leader of the Apostles and made him "the rock" (Peter) of certainty on which the Church on earth was built, making it his job to "confirm your brothers in their faith" (Luke 22,32). The bishops are the successors of the apostles who teach, administer the sacraments, and govern the Church on earth. They are shepherds of God's people on behalf of Jesus who is "The Bishop and Shepherd of our souls" (1Peter 2: 25).
In order to be part of the Catholic Church, the bishops must believe and act in communion with the Pope who is the successor of Peter. When he teaches in a solemn way about issues of faith or morality, especially when things are in dispute, his teaching is guaranteed to be infallible. This is really the infallibility of Jesus as God made man who lives in his Church through the Holy Spirit.