Why does Giles Corey accuse Thomas Putnam of "... killing his neighbors for their land?"
At this point, Giles Corey believes that Thomas Putnam is having his daughter cry witch against people on purpose.
Once a person is hanged for witchcraft, his land is taken away and is auctioned off to the highest bidder. It cannot be left to family of the hanged person. Thomas Putnam was one of the few men in Salem who had the means to buy the property. Giles feels Putnam is so greedy for land that he is willing to have his neighbors hanged for witchcraft to get it.
Later, Giles Corey found a way to get around this law. He refused to answer the indictment (accusation) of witchcraft against him. He would not answer yes or no to the accusation. Since he wouldn't answer, the court couldn't take his land away, and Giles was able to pass it down to his son. Instead of being hanged, Giles was "pressed to death" by having heavy rocks placed on his chest until he died. They were trying to get him to answer the indictment.