What are some reasons that John Proctor is to blame for the crisis in Salem in The Crucible by Arthur Miller?
John Proctor is just a victim of the circumstances that prevailed at the time. It is highly unlikely that he could have mitigated the crisis that was unfolding. Although he had his own misgivings that warranted his confession, his statement did not make any difference. He admitted to lechery, an embarrassing offence, in open court, but his confession had no effect. He was also privy to information that Abigail and the other girls were just acting; however, he had no one to corroborate the information because Abigail divulged this when they were alone.
Additionally, the entire process was skewed to punish a certain faction of the society that John belonged to, and the authorities supported the events. Although it was in the public domain that the girls were discovered dancing in the woods, all the attention was directed at the witch hunt. Thus, it is clear that those accused had their fates sealed.
John Proctor can only be blamed for being in the wrong faction. His group was outmatched by the likes of Putnam to disastrous effects.
Part of the reason that John Proctor is to blame for the events that take place in Salem is that, for a long time, he prioritizes his reputation over his integrity. To admit what Abigail told him -- that the girls are lying -- he would have to disclose the illicit relationship he had with her, and he cares more about keeping his good name, evidently, than clearing anyone else's (until it is his own wife's, and then it is too late). He feels like a fraud -- Miller tells us so when Proctor is first introduced -- but it is important to him that no one else think of him this way. It isn't until the end of the play, when all the damage is done, that he privileges his integrity: he goes to the gallows, unwilling to confess a lie to save his life, and so he finally finds his goodness. However, had he cared less early on about what others might say, how they might view him differently if they found out he wasn't a saint, a great deal of trouble could have been avoided.
John Proctor, like just about everyone else in Salem, has allowed his identity to be shaped to a large extent by his environment. That being the case, he's more concerned with defending his good name and standing in the community than in always doing the right thing. John certainly has the wherewithal to stand up and challenge the madness and the hysteria that has descended upon the town, but he chooses not to. His identity as a member of the Proctor family is more important to him than defending the truth. Indeed, it's notable that, at the end, when John signs a false confession, he only recants in order to preserve the family name.
John's valuation of his family's good name above all else proves to be a somewhat blinkered attitude, one that enables the fires of hysteria to rage more fiercely in Salem, ultimately leading to tragedy both for himself and for his family.
I think you have the two best reasons already listed, but another one could include that John Proctor is guilty of the sin of Pride. He has alientated himself from the church, and made enemies of some townspeople such that he has both ruined his credibility and made himself and his wife an easy target. He doesn't like the Minister and says so openly, was in border disputes with Mr. Putnam, and through his own personality and actions made it so he was less likely to be believed when he did come forward. While this may not have been intentional, as he could not have known the crisis that was coming, when added to the adulterous situation with Abigail, it made it very difficult if not impossible for him to stop the Court from condemning the accused, his wife, and in the end, himself.