Why was Thomas Cranmer killed?

Thomas Cranmer was executed in 1556 primarily for his role in the English Reformation and his support for Protestant reforms. As the Archbishop of Canterbury, he played a significant part in establishing the Book of Common Prayer and the doctrine of the Church of England. After the accession of Mary I, who sought to restore Catholicism, Cranmer was arrested, tried for heresy, and ultimately burned at the stake for his beliefs and actions against the Catholic Church. His martyrdom made him a symbol of Protestant resistance.