Those who are against David celebrate his troubles and failures. The term translated in the ESV as "appalled" most literally implies desolation.

This is a term of exultation over another; a word of rejoicing at the calamities that come on another; an act of joy over a fallen enemy.

Let them be desolate for a reward of their shame. Of their shameful wishes, words, and actions, as they were: their habitations in Jerusalem were desolate.

It expresses the psalmist's deep desire to see his enemies brought to shame and desolation for their actions.

David here refers to some past experience in which God rescued him from what appeared to be certain death.

The psalmist's prayer for the defeat of his enemies is based on the conviction that, in opposing him, his enemies are showing their hostility toward Yahweh ...

Psalms 40:15 Meaning and Commentary. Psalms 40:15. Let them be desolate for a reward of their shame. Of their shameful wishes, words, and actions, as they were ...

If Christ has triumphed over our spiritual enemies, then we, through him, shall be more than conquerors. This may encourage all that seek God and love his ...

shame (the feeling and the condition, as well as its cause); by implication (specifically) an idol -- ashamed, confusion, + greatly, (put to) shame(-ful thing).