What happens when Reverend Hale states that Abigail has always seemed false to him?
Not only is Hale dismissed by Danforth, but at that moment the girls go full fledged into their hysteria witchcraft act, accusing Proctor. Abigail begins the hysteria with a weird scream and the other girls join in. I believe that Abigail was threatened by Hale's remark and wanted to divert attention from him. Furthermore, since she now perceives that her plan to gain Proctor by accusing his wife was not going to work, she wants to gain revenge by accusing him. By the time Hale is able to get another word in, the moment is lost. Any chance he had of being heard by Danforth was over once the girls started their act.