In Elizabeth George Speare's award-winning young reader's novel The Witch of Blackbird Pond, prior to the moment the mob decides to storm Hannah's house, a great deal happened to upset the colony of Wethersfield.
First, political turmoil erupts. King James II threatened to revoke the colony's charter because the colony questioned the king's authority over the colony, wanting total control of its own government. The governor of Massachusetts, Governor Andros, however, sides with the king. At one point, in Chapter Fifteen, British troops arrive in Wethersfield to discuss the charter, but the colonists steal the charter in an attempt to keep it from being revoked. Regardless, Governor Andros still suspends the charter.
Soon after the difficulty with the charter, in Chapter Seventeen, a plague hits the colony. Mercy is among the sick who are deathly ill. Though Dr. Bulkeley, the reverend, applies a poultice of onions that breaks her illness, a mob approaches Uncle Matthew's house declaring that three have died from the plague and blame the plague on Hannah:
It's the witch's doing! ... The Quaker woman's. Down by Blackbird Pond. She's been a curse on this town for years with her witchcraft! ... We should have run her out long ago.
Fortunately, Kit is able to rescue Hannah from her cottage and hide her in the bog just before the mob sets fire to the cottage.
Hence, as we can see, though the plague was the main reason why the mob decided to accuse Hannah of witchcraft and storm her home, the whole colony's emotions were tense as a result of having its charter suspended. Had the plague happened prior to or without the backdrop of political turmoil, the colonists' emotions might have remained calmer.