This whole chapter is a funeral song about the state of things in the royal household. They're singing the funeral songs of three kings of Judah while they're still alive. God is telling the exiles in captivity not to look to Zedekiah to deliver Jerusalem and reminding them that God is their only hope.
Do we encourage people to hope in things that are temporary? The only sure hope we have is Christ. If the grace of God is not your hope, you have a false hope and are disillusioned. You must look to the Lord continually.