While Abigail Williams certainly shares responsibility for the deaths of innocent villagers, Miller does not dogmatically argue that she is the reason that they died. At any point during the trials, the judges could have stopped them. John Proctor could have spoken up immediately about Abigail's confession that the girls were merely "sportin." Rev. Hale could have protested earlier and more passionately when he had his first inkling that something was amiss. And, Rev. Parris could have put aside his pride and prevented the trials completely if he had explained to the town what his niece, daughter, and other girls were doing in the woods.
This is Miller's point--that a witch hunt (literal or not) involves a group of people acting irrationally out of fear (and in this case--greed and pride). One person is not solely the reason for the deaths in Salem--just as Joseph McCarthy was not the only person responsible for the Red Scare. Congress could have refused to go along with its hearings at the time, and Americans could have focused on logic rather than an exaggerated threat.