Why is Thomas Putnam such a bitter man in The Crucible?
Thomas Putnam has many reasons to be bitter--at least according to him! He is "one of nine sons" who have put "the Putnam seed... [in] this province," but only one of his eight children has managed to survive past childbirth. To add insult to injury, his brother-in-law was not chosen to be the minister of Salem, which Putnam perceives to be a slight to his family and his reputation by the community at large.
Although already part of one of the wealthiest families in Salem, Putnam had once tried to break the will of his father (which bequeathed the greater share of wealth to Putnam's step-brother); this, too, tarnished his honor in a public manner.
With these grievances in mind, Putnam takes every opportunity possible to further advance his own agenda; knowing that those who are convicted in the witch trials will no longer legally be able to own land, he intends to have as many individuals as possible found guilty so that he may purchase their property at a highly discounted rate. Putnam convinces his daughter to accuses Giles Corey's wife of witchcraft. This eventually comes to light when Corey realizes that, "there is none but Putnam with the coin to buy so great a piece," and that, "[t]his man is killing his neighbors for their land!"
Thus, Putnam contributes to the panic around the trials out of greed rather than true religious conviction... which, too, is a mark of his embitterment. Putnam is ready to sacrifice the human lives of those he resents in order to elevate his social and economic standing in Salem.
Thomas Putnam is bitter for two reasons that come together in the accusations surrounding the trial. First, he feels he's been done wrong—that neighbors and community members have taken advantage of him over the years. This makes him ready to lash out. Second, he's ambitious, specifically materially ambitious. He wants to be a rich landowner. Well, both the way people have done him wrong and the general focus of the community get in the way of this. So, both his nature and his context contribute.