Who is to blame in the Crucible?

I think the Puritans themselves, especially the leadership, are to blame. The people of Salem were full of hypocrisy and petty squabbles. They fuelled their own paranoia letting Abigail and the girls manipulate them with bizarre stories. They also let the witch court kill many innocent people. If you are looking for one person, I might consider Abigail caused the most upset.