The conclusion about tituba throughout the whole play and how the character ended up in act 1? with the evidence.

Tituba is no fool. She knows there isn't away out for her. She is a slave girl and Abigail's haphazard condemnation is enough to make her a scapegoat for this whole thing. Tituba instead confesses readily and names other people "allegedly" involved. This takes the attention off her and puts her in better standing with the court.