Greed, revenge, mass hysteria and superstition contribute to the insanity in Salem in a variety of ways. What the witchcraft hysteria succeeds in doing in Salem is bringing out the most primal forces in people, some of which are quite evil.
For example, the Putnams are motivated by both revenge and greed to use the insanity in Salem for their own purposes. Thomas Putnam has his daughter Ruth accuse Mr. Jacobs of witchcraft so that his land will be put up for sale. It is so convenient that Thomas Putnam, the richest man in town, happens to live next to Mr. Jacobs and would benefit greatly by being able to buy his land at a reduced price.
Mrs. Putnam takes revenge on Rebecca Nurse because Mrs. Nurse is a mother and grandmother many times over and has acted a Mrs. Putnam's midwife. Mrs. Putnam's seven babies all died shortly after birth, so she blames Mrs. Nurse and accuses her of bewitching her babies after they were born. Mrs. Putnam needs to believe that her babies were bewitched, she cannot accept that she has only one living child, Ruth. The same can be said of Mr. Putnam who declares that he is one of 11 and it could not possibly be his fault that the seven babies died because they were sickly, his family is strong and healthy.
Abigail Williams uses the witchcraft hysteria in the most evil way, by trying to get rid of Elizabeth Proctor because she is in love with John Proctor. She sets up a charade with a pin hidden in a doll made by Mary Warren, and then pretends to have been stabbed by the spirit of Elizabeth Proctor.
Elizabeth is accused of witchcraft and jailed. She is not executed because she is pregnant.
Superstition plays a strong role in the play as well, because there was so much that these 17th century people did not understand about the weather, disease, and how the human body works. Anything that they did not understand they attributed to the will of God, or the work of the devil. So when they get the idea that the devil is at work in Salem, it spreads like wildfire throughout the community and becomes a self-fulfilling prophecy.
The evil that is perpetrated on the innocent accused is, in fact the work of the devil, it is evil, not because the devil himself is present, but because humans are capable of evil all by themselves. And, that is how the insanity in Salem in 1692 seeps into the very fabric of the lives of everyone in the town.