The Puritan people were not suppose to be greedy or sinful so they had to cover up those feelings well to become accepted members of the community. Yet those feelings were still there; resentment, greed, jealously of their fellow members of their community bubbling just under the surface.
Witches gave these people a "socially acceptable" way to fence their frustrations and succumb to their real feelings. I believe that a majority of these people knew the "witches" they "outed" were not actually witches. They cried witch because it suited their needs; either due to long held grudges or their desire to acquire some possession the "witch" currently had.
The Salem witch trials were a way for greedy, begrudged people to gain an upper hand in a way that not only was accepted in their society, but considered noble. Outing a witch not only allowed a person to gain whatever profit they sought, but also increased their standing in the community.