Their anger resulted from frustration. It was just a runaway condition that upon being brought to a halt made everyone happy. Joy came to the family. Order restored will eliminate the anger and hostility provoked by circumstances, but parenting doesn't stop with conditioning children to outward obedience. Joy is a positive virtue, not just the absence of conflict.
Some parents are joyless regardless of the circumstances.
They may not be angry or unhappy, just joyless. Look at it as a scale. Anger or bitterness is on the far left. A stable, sedate personality is in the middle, and joyfulness is on the far right. Granted, children do far better with deadpan parents who have no joy than they do with angry or bitter parents, but they do best when both parents are known for their joy.