About 3,000 rebels are thought to have been killed at Dussindale, with Warwick's army losing some 250 men. The morning after the battle, 28 August, rebels were hanged at the Oak of Reformation and outside the Magdalen Gate. Estimates of the number vary from 30 to 300. Warwick had already executed 49 rebels when he had entered Norwich a few days before. There is only one attested incident in which the rebels had killed in cold blood: one of Northampton's Italian mercenaries had been hanged following his capture. Kett was captured at the village of Swannington the night after the battle and taken, together with his brother William, to the Tower of London to await trial for treason. Found guilty, the brothers were returned to Norwich at the beginning of December. Kett was hanged from the walls of Norwich Castle on 7 December 1549; on the same day William was hanged from the west tower of Wymondham Abbey.
Question: Why was Kett and William hanged?
Answer: treason