SimchaMinute by Rabbi Avigdor Miller
Some persons emerged from the concentration camps tzaddikim gemurim (perfectly righteous) because for the first time in their lives they were able to think fundamentally, they were divested of all the hindrances of materialism.
Their tribulations made them understand that this world even in its best state is nothing... These people, those who survived, or those who went with such a frame of mind to the gas chambers, became great characters, great neshamos, as a result. — Emunah and Patience (#380)