Deindividualization is associated with what is sometimes called "group think" and can explain why people do things in groups that they may never do outside of that group.
In Miller's "The Crucible", when the villagers in Salem Village begin to accuse their neighbors of witchcraft, mobs are formed where people, some of whom are highly respected, are forcibly dragged out of their houses, tortured, hanged, and almost ritually humiliated. John Proctor is one of the characters who maintains his own individuality within the mayhem, but when he tries to make the village see that they have been fooled by the accusing girls, they turn on him.
Few of those within the mob would have contemplated the actions taken once the accusations began.
Scapegoating, as a psychological term, could be applied to what happens to each of those villagers accused of witchraft. For instance, Miller, in his commentary before Act I states, if a man says that "Martha Corey had come into his bedroom at night, and that, while his wife was sleeping at his side, Martha laid herself down on his chest and 'nearly suffocated him'", he can scapegoat Martha in his sin (whether it was mental or actual).
There are many other examples of scapegoats within the play: Tituba plays one for Abigail, Proctor for not going along with the croud, and all of the accused are scapegoated for whatever is going wrong in the town.