2 Chronicles 36:14-21
"Furthermore, all the officials of the priests and the people were very unfaithful following all the abominations of the nations; and they defiled the house of the Lord which He had sanctified in Jerusalem." - v14
Throughout the ages, it seems that God's people have always been surrounded by cultures that were desperately wicked. While I know that this is probably so that others may come to know Him through the example of His people, but it is truly difficult to live in close proximity with other people without absorbing some of their attitudes, traditions, and ways of thinking. That is what happened to Israel in this passage. They had begun to live the way others lived and broke God's commands, which were intended to protect them and to set them apart as holy - God's own posession.