Why did God open the windows of heaven and bring the age of grace?

Les teaches that Israel came up through their history with a glorious prospect, but they blew it, dropped the ball, and rejected their Messiah and the promised Kingdom. Because of that rejection, God did something different: He opened the windows of heaven and brought what we call the grace of God. In this age of grace, all we have to do is believe the Gospel, and God does everything else—unheard of through the previous thousand years of human history. The age of grace has ended, and God will pour out His wrath in the final seven years of dealing with Israel's prophecy, followed by the final thousand-year millennial reign under Christ's perfect rule.