Thus says the Lord:
“For three transgressions of Judah,
and for four, I will not revoke the punishment,
because they have rejected the law of the Lord,
and have not kept his statutes,
but their lies have led them astray,
those after which their fathers walked.
What is sad in this declaration is that Judah has become just as guilty of the same sins as the ungodly country, Moab. They have rejected God's revealed ways for living, have stopped following God's commands and begun following lies.
While it's true that all of God's wrath was placed on Christ at the cross, God also visits the church with purifying judgements (1 Peter 4:17). A person's belief in Christ may assure their eternal salvation, but they may or the people may corporately have sin that God must deal with when he visits. What I mean is that God who is completely holy and just must deal with sin. Sin that is placed on the cross is dealt with and God is completely satisfied with his forgiveness for it. But sin that has not been repented of is what is "sticking out" and must be whacked. See 1 Corinthians 3:13-15 and 1 Peter 1:6-7.