What is the main thing that keeps the morals of Salem from deteriorating?

The main thing that ends the trials is the stoic goodness and morality of specific characters. The hysteria brought on by the girl's actions had far reaching implications. Their accusations ran rampant and filled the community with a fear that deteriorated not only their ability to rationalize but their emotional stability as well. The weakest qualities of the people in the community gave into their good sense, but there were those that even in the face of adversity, who held onto their own moral compasses and faith in humanity. These were the people who eventually ended the hunt and the senseless murders of innocent people.