Why did Charles dickens call a Christmas carol a sledge hammer to society?

He wrote it as a call to change the culture. He was living at the industrial revolution. This transition from agriculture to industry was not smooth with protections in place for the more vulnerable population.The poor, especially the poor's children had no rights, and the safety nets provided for the poor where workhouses, the conditions were harsh there, by design to discourage anyone form utilizing the service. Children were separated from parents, and siblings and put in equally horrible orphanages and were essentially sold as indentured servants (slaves). He was using the Carol to call on us to give philanthropically, but not only by giving monetarily but of ourselves- to care who it's for, to know who it's for and to give the voiceless voice.