Why was witchcraft such a major crime anyway? who was it a crime against exactly?

Witchcraft was a major crime bc in the time period religion was very popular in all aspects of society. witchcraft was viewed as satanic and evil

Witchcraft was something that scared people.  It was seen as unholy and unnatural.  It not only went against religion, but it went against the way of life. In history, when anything threatened the leaders of the time, they would freak out and make laws preventing the subject.  Witch craft was another one of those things.  If people could do witch craft, they could take over.  They wouldn't have to follow the law or rules.  They could do whatever they want.  And witch craft was believed to be taught.  So you could get followers and a group of people would take over and be stronger as whole.  But it was also seen as a possession.  Like if a devil took over your body.  That went against God. And although people say there was separation of Church and State, a lot of the laws are, and were, based on religious views. 

Answer for apex - the reformation