Because they believed that the devil was acting through witches and they believed that the devil was acting in their territories.
Explanation:
The New England region promoted many adverse situations for the colonists. The cold climate, the conflict between two native tribes in the region and the spread of smallpox cases made Puritan settlers believe that the devil was close to the region and that he would continue to act negatively on their lives.
For them the devil was able to act through witches and as the population was facing many problems (in addition to the many deaths that occurred), they began to distrust each other, which initiated a vast and crazy search for witches and signs of witchcraft in the population.
