Why did people accept the Twelve as apostles but question Paul's apostleship?
People accepted the Twelve because their unique position with Christ and His earthly ministry was readily understood and recognized. Paul, however, had been a raging opponent of Jesus of Nazareth, so his apostolic authority was repeatedly challenged and he had to defend it.
Les explains that Paul, writing to believers at Rome, calls himself the apostle of the Gentiles and magnifies his office, refusing to take a back seat to anybody concerning his apostleship. When teaching Paul’s other letters, such as Galatians or Ephesians, Les notes that Paul is always having to defend his apostleship. That is understandable because people can readily understand the Twelve and their unique position with Christ and His earthly ministry, and they have no problem recognizing their apostleship. But Paul came as one who had been like a raging bull fighting against everything that spoke of Jesus of Nazareth. That contrast explains why the Twelve were readily accepted while Paul’s apostleship was questioned.