Why did God not expect Peter and the apostles to know about the Church age?
God did not expect Peter and the apostles to know about the Church age because He had kept it a secret hidden in His mind, not revealed in the Old Testament or Gospels. During early Acts He was still giving Israel opportunity to repent, while Peter operated only on the revealed Old Testament program.
Les explains that the rapture, the Church, and Church doctrine are not to be found in the Gospels or the Old Testament, because they are a secret held in the mind of God. At that time God was dealing only with the nation of Israel. Peter and the other eleven apostles therefore operated only on what God had revealed, which was the Old Testament program. Peter had no concept of God turning to the Gentiles for 1900 and some years; none of them did, and it wasn't their fault. God didn't expect them to know because He had been holding it a secret, while giving Israel every opportunity to repent of what they had done to their Messiah. After Israel kept rejecting the offer of the King and the Kingdom, God moved that program into the future and inserted an undetermined period of time, after which the seven years will come, Christ will return, and the King will set up His Kingdom.