Why did the Apostles ask Christ who was the greater among them, if they knew that Peter was the greater?

The Catholic Answers

They were disputing as to who should be the greater in Heaven, not concerning their office on earth. The fact that Christ replied by teaching a lesson of interior humility shows that He knew them to be referring to their personal standing in God’s eiteem.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty