Why did God postpone the offer of the King and the Kingdom?
God postponed the offer of the King and Kingdom because Israel kept rejecting it after Christ ascended. He therefore moved that program into the future and inserted an undetermined period of time, after which the seven years come, Christ returns, and the King establishes His Kingdom.
Les explains that as soon as Christ ascended, Israel kept on rejecting the offer of the King and the Kingdom. So God moved all of this out into the future and put in an undetermined period of time. No one knows when it will end, and then the seven years will come, then Christ will return, and then the King will come and set up His Kingdom. Les also notes that Peter and the other eleven operated only on what God had revealed, the Old Testament program. Peter had no concept of God turning to the Gentiles for 1900 and some years. God had been holding it a secret and was giving Israel every opportunity to yet repent of what they had done to their Messiah.