The immediate cause of the Intolerable Acts was the Boston Tea Party, in which colonists dumped a large shipment of British tea into the Boston harbor in protest of the Tea Act. The British government considered the Tea Party an act of rebellion and responded with the Intolerable Acts, which were designed to punish the colonists and assert British authority.
Assertion of British Authority
More broadly, the Intolerable Acts were part of a larger effort by the British government to reassert its authority over the colonies. The British had been increasingly frustrated by the growing resistance of the colonists to their policies, and the Tea Party was seen as the last straw. The Intolerable Acts were intended to send a clear message to the colonists that the British government would not tolerate any further defiance.