What is being described here is public mourning. Moab is in desolation... a judgment that God has ordained. And the result of the searing loss is public mourning. The historic foe of Israel is brought low.
The practice of public mourning seems strange to me as an American. My culture keeps grief quietly. We don't display it with any flair. Even a funeral for a loved one is often a private affair. There are exceptions, like national tragedies, but even then the mourning is more somber and subdued. Flags are lowered to half mast. Trumpets play taps. It is hushed and the idea of sackcloth, ashes, and wailing does not enter our minds. We dress in our finest, look our best, parade the dress uniformed soldiers, and quietly reflect. Overt public mourning is not really a Western experience. It is quite foreign to us.
So when the Bible uses language like this, we struggle to relate. But the emotion expressed as Moab falls is real. A people acknowledge the desolation and destruction. Emotion attends public mourning for them. Moab was warned by God's prophet that it was coming. And even mourning can have the purpose of turning the heart to consider God.