Why do Catholics believe the Catholic Church is the one true Church, founded 2000 years ago by Jesus Christ himself?

The Catholic Church is the only church today that can claim to be the one church founded by Jesus Christ 2,000 years ago. Other denominations can trace their origins back to various human founders at a later date in history. 

In Matthew 16:18, Jesus said to Peter, “And I tell you, you are Peter, and on this rock I will build my church, and the powers of death shall not prevail against it.” Jesus handed the authority to guide the Church in His name to Peter and the apostles, to be passed down through the centuries. The Church is the body of Christ (Ephesians 5:23). Christ established only one Church—one body—so that there would not be multiple “bodies” with conflicting doctrines. After all, God cannot contradict Himself. Christ also wanted His Church to be visible, so all may see that the Church is indeed one, just as Christ and the Father are one (John 17:22). 
 
This one, visible church, with divine authority and consistent doctrine that Christ established 2,000 years ago is the Catholic Church, the pillar and foundation of truth (1 Timothy 3:15). As Paul asks in 1 Corinthians, “Is Christ divided?” (1 Corinthians 1:13). No. That is not what the Christ intended. So, He established one Church.