The Salem Witch Trials, as depicted in Arthur Miller's play "The Crucible", examined many different aspects of revenge and hysteria.
Many of the townspeople would accuse others based upon reasons only understood, then generally assumed by others, by the person making the accusation.
It was very easy to accuse people in the town given the mass hysteria which broke out during this period. People would accuse others based upon fear (that they themselves would be accused--so why not accuse another before another person could accuse them), revenge, and jealousy.
In regard to Putnam, he knew that by accusing Nurse of witchcraft the possibility of her land being claimed by the township would be greater. It was most likely his hope that when this happened he would be able to purchase the land without issue. Therefore, like many others, Putnam used the hysteria of the accusations in Salem to his benefit.