What point did Stephen make about Christ's second coming to the Jews?

Stephen taught that Christ's second coming to Israel was ready to occur as soon as the Jews believed He was their promised Messiah, with no 2,000-year interval anticipated. After His death, resurrection, and ascension, everything was set for Him to return if Israel would simply believe.

Les explains that Stephen rehearses Israel's history to drive home the point that Christ came the first time in His earthly ministry, and Israel rejected Him. But now, after His death, resurrection, and ascension, He was ready to come the second time if Israel would just believe He is who He says He is. Stephen, like the Jews of that day, did not see a 2,000-year interlude; he expected the Lord's return to be imminent upon Israel's national belief. This fits the typology of Moses in Acts 7, where Moses supposed his brethren would understand that God would deliver them by his hand.

What point was Stephen making about Jesus' first and second coming?

Stephen was showing that Israel's rejection of Jesus at His first coming did not cancel God's program; the Messiah had died, risen, ascended, and was ready to return the second time if Israel would believe He is who He claimed to be. Stephen, like the Jews, did not envision a 2,000-year interval.