Why do so many people in this society add to the harm and add to the icing on the cake? The weaker people are, the more they want to bully and laugh at them.

This has to mention human nature. All human nature is downward. People who fall when they are down just want to show their poor sense of superiority by bullying and mocking others, and those who add icing on the cake just want to show their faces on others for later use.