No. It should not be surprising when the accusations against certain people of the town begin to multiply. The reader sees at the end of Act I that the girls are willing to accuse innocent people; however, all the girls accuse different people. The names shouted out at this time are Sarah Good, Goody Osburn, Bridget Bishop, George Jacobs, Goody Howe, among others. The girls, at this point, have not had time to discuss or even observe one another in the process of accusing men and women of the town. They are unsure what the reaction of the townsfolk will be.
However, as the play progresses, these accusations multiply. Originally, it is Abigail who accuses Sarah Good of witchcraft, but in Act II, Mary Warren has also accused her of the same crime. Mary Warren speaks of Sarah Good saying, "She sit there, denying and denying, and I feel a misty coldness climbin up my back. . . . Last month, she walked away, and I thought my guts would burst for two days."
This is not surprising, because the reader can deduce that most people accused at the beginning of the play are people who are deemed unimportant by most of the town. Elizabeth and Mary both mention that Sarah Good mumbles frequently, that she is old and sickly. She and others are easy targets.
The downfall of the girls happens when they begin to accuse more upstanding members of the town--those like Rebecca Nurse and John Proctor. Reverend Parris says in Act IV:
"It were another sort that hanged til now. Rebecca Nurse is no Bridget Bishop that lived three year with Bishop before she married him. John Proctor is not Isaac Ward that drank his family to ruin. I would to God it were not so, but these people have a great weight yet in the town."
Those who are weak are easy targets, which is why there are multiple accusations for those types of characters.