John 10:10. The thief cometh not, but for to steal, kill and to destroy: I am come that they might have life, and that they might have it more abundantly.
As of your question, I believe the devil tries to steal our joy. There is only one true judge and that's God. Only he knows why people do the things they do and what is behind the situation.
I did some research and can not find anything. I'm still learning myself so I may be missing something.