The 12 apostles represent the 12 tribes
Paul, a Jew with Gentile citizenship, was one man who represented the one body in Christ (the Church)
Jesus kept the message of Grace, delivered by Paul, separate from the message of the kingdom (offering Christ to the Jews) which was delivered by the 12 apostles
The kingdom message had been (temporarily) replaced by the mystery of the Church
The kingdom message will resume when the Body is complete