Why will Israel be the greatest nation in the Millennial Kingdom?

Les explains that two classes of people enter the Kingdom. The first is the remnant of Israel, and because it will be the largest single segment nationally, Israel will be the greatest nation in the Kingdom Age. The second class is surviving Gentiles; out of all those Gentiles, only a small number from each Gentile nation enter. Les suggests, though he cannot prove it from Scripture, that those Gentiles will return to their homelands and become seed stock as believers for the new generation during the thousand-year reign of Christ. During that reign Satan is locked up, there is no sin, and Christ is the absolute ruler—a benevolent dictatorship, as Les calls it. It will be a glorious time, and since there is no sin, sickness, or death to speak of, there will be a massive population explosion, perhaps rivaling the period between Adam and the flood. The curse is lifted, including the pain and travail of childbirth.