In The Crucible, why does Abigail Williams accuse people at the end of Act 1?
Abigail has been through a lot in this first act. First, she dealt with the suspicions of her uncle, the Reverend Parris, and his concerns about her activities in the woods as well as her reputation in the town. Next, Mary Warren insists that they have to tell what they did in the forest, and Abigail's cousin, Betty Parris, calls her out for drinking a "charm to kill Goody Proctor" and not confessing it. Then, her old flame, John Proctor, arrives, and she must listen while he tells her that their affair is over although she still loves him. Then, the Reverend Hale questions her, "grasping" her arms, clearly suspicious of her and what she seems to be hiding. Ultimately, she accuses Tituba, it seems, in order to deflect attention and suspicion from herself; she knows her word will be taken over a slave's any day, and she is desperate to escape the negative attention focused on her thus far.
However, then Hale begins to speak gently to Tituba, "tak[ing] her hand" and telling her that she is "God's instrument put in [their] hands [...] to help [them] cleanse [their] village." He tells her that she has a special purpose, making her feel special, and so she accuses Goody Good and Goody Osburn, perhaps, to please him and to make her story seem more believable. The room is electrified, and people instantly believe Tituba. Abigail seems to sense an opportunity -- stage direction states that she is "staring as though inspired" -- and suddenly she, too, confesses, repeating Tituba's two accusations (for credibility) and adding one other. She has an opportunity, here, to gain power in her household and in the town through her accusations. In addition, when she eventually accuses Elizabeth Proctor (the thought of which is perhaps what "inspired" her), she has the chance to get John all to herself. She can also accuse anyone in the town, and she is likely to be believed: anyone who's ever spoken out against her, anyone she simply doesn't like, and so on. Hysteria seems to take over when Betty chimes in with her accusations, and she and Abigail name many more "witches" before the act ends.