Why do people always go after the wrong person

Everytime someone does something bad and you search up that user you always see another person saying they are getting hate for no reason/they are the wrong person. I don't how when people want to hate someone they don't do any research and just hate the first person that pops up. It just shows that hate is a crowd mentality and if someone says hate people hate blindly. (I am not defending bad people just saying do some research before hating.)