Why was Paul given authority to write the epistles that became central to the Scriptures?

Les teaches from Colossians 1:25-26 that Paul was made a minister according to the dispensation of God given to him, to fulfill or complete the Word of God. The mystery, the secret hidden from ages and generations, was now made manifest. Les explains that all these Pauline truths were held in the mind of God; Israel never had a concept of them, and the Twelve had no concept of them. Then Saul of Tarsus, this renegade, was saved by grace, and to him God revealed the secrets, the mysteries. That is why Paul was given the authority to pen the epistles that became the central part of the Scriptures: he is the one to whom God revealed the mysteries.