All fall short…

But they would not listen, but were stubborn, as their fathers had been, who did not believe in the Lord their God. They despised his statutes and his covenant that he made with their fathers and the warnings that he gave them. They went after false idols and became false, and they followed the nations that were around them, concerning whom the Lord had commanded them that they should not do like them. And they abandoned all the commandments of the Lord their God, and made for themselves metal images of two calves; and they made an Asherah and worshiped all the host of heaven and served Baal. And they burned their sons and their daughters as offerings and used divination and omens and sold themselves to do evil in the sight of the Lord, provoking him to anger. Therefore the Lord was very angry with Israel and removed them out of his sight. None was left but the tribe of Judah only. (2 Kings 17:14–18)

When reading passages like this one, a question comes into my head that would horrify most Christians. Did God “remove” Israel out of His sight for rejecting Jesus by using the horror of the holocaust? 

This question is considered a theological interpretation rather than a widely accepted scriptural doctrine because there is no evidence in the NT that God would deal with His people that way. His desire was that the good news of salvation through faith in Jesus Christ would go out to the world, to the Jew first and then the Gentiles. When the first disciples followed that pattern, eventually the people of Israel rejected it, so they turned to the Gentiles.
And Paul and Barnabas spoke out boldly, saying, “It was necessary that the word of God be spoken first to you. Since you thrust it aside and judge yourselves unworthy of eternal life, behold, we are turning to the Gentiles. For so the Lord has commanded us, saying, “ ‘I have made you a light for the Gentiles, that you may bring salvation to the ends of the earth.’ ” And when the Gentiles heard this, they began rejoicing and glorifying the word of the Lord, and as many as were appointed to eternal life believed." (Acts 13:46–48)

Many see the holocaust as only about the Jews. But besides, the six million Jews who were murdered, others were also put to death who had no historical involvement with the crucifixion. The only commonality is that all are sinners just as I am even though Roma and Sinti were targeted on racial grounds, people with disabilities were considered "unworthy of life" and a threat to genetic health, Polish and Soviet Civilians, Soviet Prisoners of War, political opponents such as Communists, Socialists, and Social Democrats, Jehovah’s Witnesses, homosexuals, “Asocials" and Social Outsiders including the homeless, prostitutes, alcoholics, and those deemed to be "professional criminals” as well as black people, and anyone else considered "racial enemies," "biological threats," or "enemies of the state” were targeted. 

As for all being sinners, the NT says, “the righteousness of God through faith in Jesus Christ is for all who believe. For there is no distinction: for all have sinned and fall short of the glory of God. . . .” (Romans 3:22–24) 

Another issue is that the OT speaks of unbelieving people who prosper in this life, yet will not have eternal life, yet their ‘punishment’ for rejecting God is not mass execution, but an eternity in  torment.

Not everyone thinks this was a horrible event. A Jehovah Witness (a cult that imitates Christian without faith in Christ) told me that they feel honored to have been “persecuted for their beliefs.” While that seems weird, it is a NT truth that those who believe in Christ (which excludes cults) are to rejoice when others persecute them:

“Blessed are you when others revile you and persecute you and utter all kinds of evil against you falsely on my account. Rejoice and be glad, for your reward is great in heaven, for so they persecuted the prophets who were before you." (Matthew 5:11–12)

Certainly the ways of God are above our normal ways of thinking. Yes, it is horrible that millions of people were put to death by others who hated them for various reasons, yet thinking God allowed this to happen to punish them does not make it right. I tend to agree with those who say that we ask the wrong question. Instead of trying to figure out why some are being punished and others receive eternal life, we should wonder why anyone is saved. 

Jesus, when Christians decry the evil that others do, it is best that I respond with, “Yes, yet I am a sinner too” and praise You for Your mercy in forgiving me and giving me life. I don’t want to use the sins of others in an effort to make me look more righteous than they are. Except for Your amazing grace, all deserve to die.