One of the reasons to doubt the accusations is the fact that they are being made by Abigail Williams. Abigail is a known liar, and she has a clear motive to lie in this situation. She is in love with John Proctor, but he is married to Elizabeth Proctor. If Abigail can accuse Elizabeth of witchcraft, she will be able to get rid of her and marry John.
Another reason to doubt the accusations is the fact that they are being made against people who are generally well-respected in the community. The people who are accused of witchcraft are all pious, upstanding members of society. There is no reason to believe that they would suddenly start practicing witchcraft.
Finally, the way that the accusations are being made is suspicious. The accusers are often in a trance-like state, and they seem to be speaking in tongues. This suggests that they may be being influenced by some outside force, such as the devil.
In conclusion, there are many reasons to doubt the accusations that are made at the end of Act 4 of The Crucible. While it is possible that some of the accused may be guilty of witchcraft, it is also possible that they are innocent victims of a malicious plot.