How can the bystander make the bullying worst?

By being a bystander you are witnessing the event occur but you are not taking place into it. So when someone witnesses bullying and they do not say anything to stop it then they are making the situation worse because they show the person being bullied that no one is going to defend them or protect them. That can make them feel even worst because they see they have no one there for him/her. That can lead to depression for them. As well on the person that is doing the bully sees that no one is going to stop them from hurting other people. This will push them to do it more. 

It settles nerves, reduces the tension.