They can't answer such because their reasoning is selfish and without sound basis. Their objective is to separate to lord over their fellow human "brothers", while Christ's objective was to unite.
I see it as the 12 Tribes for whom the 12 Apostles were obligated by Christ to take the message of redemption; dire lost Israel. Simple symbolic multiplication.
The Great Crowd is simply the Gentiles who were to get the same message of redemption and same prize.
And the DUH! There would be more Gentiles than Jews who would hear and believe Christ was the promised Messiah; even to this very day.