The security and nurturing they felt when both their parents used to cuddle and talk softly together with them is gone. They sense hostility and anger when they see or hear the arguements. Children soon believe that no time is the right time to approach either parent. Children feel powerless and vulnerable when this pattern emerges. Children in divorce are often alone, feeling very lonely and sad.
Children change their behavior, usually for the worse.
Misbehaving gets them attention. I'll just be bad, and they'll turn to me instead of each other. The nightmares that come later, well, I'll just deal with them in my sleep. Losing the guilt can wait, too. Right now, I just want their attention, and being bad will get it.