Why did the early churches need men gifted to teach Pauline doctrine?

Because the New Testament had not yet been written, early apostolic churches had no printed Word to rely on. They therefore depended on gifted men who could proclaim and teach Pauline doctrine directly by God's power, rather than Old Testament teaching, preventing confusion until Scripture was available.

Les explains that when Paul wrote to the Corinthians, there was still no New Testament written. The Gospels had not yet been written, and Paul's own letters had not gone out as the Word of God. These early, primitive apostolic churches were growing and reaching out in the pagan world without the benefit of the written Word. They had to depend on gifted men, gifted to the point that they could teach people the Pauline doctrines and not that which was still coming out of the Old Testament, or they would have had pandemonium. Paul, by inspiration, realized that the most important thing the local church could have was men who could proclaim the truth of God's Word without having it in print. Later, that gift would fade away because now we have the printed page.

Why did the gifted men in the early church have to teach Pauline doctrine instead of Old Testament teaching?

The early churches had no written New Testament, and the Gospels and Paul’s letters had not yet been published as Scripture. Since they could not rely on the completed written Word, gifted men had to proclaim Pauline doctrine directly; teaching the Old Testament instead would have produced confusion, or pandemonium, among believers.