Most people want to be good people, but not everyone has the tools to do that or the capacity to use those tools, so they end up doing harm instead. Generational trauma and dysfunctional family systems are the root of a lot of harm in the world. The other major factor is that the deep-seated monkey brain emotional responses we have often lead us to harm others. For example, racism is strongly linked to tribalism which is a pattern that is basically universal in social animals. Defying those instincts is difficult and requires a lot of learned emotional intelligence which not everyone has a chance to develop. A lot of our instincts encourage morally or ethically bad behavior because those instincts improved our ancestors' chances of survival, but at the cost of harming others.