Why does Miller start the play the way he does?
Miller begins the overture with the historical information that is necessary to establish the Puritan background and motivations. As the play progresses, the reader is able to realize how the panic and hysteria came about with this information.
It also give insight into Parris' actions as the play continues. The reader sees his reasons for not stopping the witch hunt, even though he fully realizes his niece, Abigail is falsely accusing people to save her own skin.
It would be puzzling for readers if the background was not given in this way, instead of the play beginning directly.
Miller intends this play to be a symbolic microcosm - a miniature version of the world meant as a comparison to the world in which he was living. Miller was very forthright about the fact that he wanted to draw attention to Senator McCarthy and the "witch hunt" of Communism that McCarthy was on. Therefore, he creates a complete world in the community of Salem, with a heirarchy and established relationships, to make the analogy more developed.