Why was the tribulation wrath and Christ's return delayed after Israel rejected the Kingdom?
Because Israel rejected the Kingdom, the King could not pour out the tribulation wrath, and Christ's return to set up the Kingdom was delayed. He had to wait in Heaven until something else glorious would come to pass, which the context identifies as Saul's conversion in Acts chapter 9.
Les teaches that Peter remained on the top timeline and in the prophetic program, preaching that the crucified One had been raised and exalted to the Father's right hand according to Psalm 110:1. The prophetic order was wrath and vexation, then Christ's return to set up the Kingdom. But because Israel rejected it, the King could not pour out the tribulation wrath; He had to wait in Heaven until something else glorious would come to pass. The narrative then turns to Acts 9 and Saul's conversion on the road to Damascus as that next development.