What things led to the canonization of Thomas More? Besides his martyrdom, what were some specific things that led to the canonization of Thomas More?
Besides his martyrdom? What were some specific things that led to his canonization?

The Homily at the Canonization of St. Thomas More in 1935 by His Holiness Pope Pius XI1 provides some of the reasons:


St. Thomas More, together with St. John Fisher were bright champions and the glory of their nation ... “as a fortified city, and a pillar of iron, and a wall of brass.” Therefore they could not be shaken by the fallacies of heretics, nor frightened by the threats of the powerful. They were, so to speak, the leaders and chieftains of that illustrious band of men who, from all classes of the people and from every part of Great Britain, resisted the new errors with unflinching spirit, and in shedding their blood, testified their loyal devotedness to the Holy See.
St. Thomas More was endowed with the keenest of minds and supreme versatility in every kind of knowledge, he enjoyed such esteem and favour among his fellow-citizens that he was soon able to reach the highest grades of public office. But he was no less distinguished for his desire of Christian perfection and his zeal for the salvation of souls.
The testimony in the ardour of his prayer, in the fervour with which he recited, whenever he could, even the Canonical Hours, in the practice of those penances by which he kept his body in subjection, and finally in the numerous and renowned accomplishments of both the spoken and the written word which he achieved for the defence of the Catholic faith and for the safeguarding of Christian morality.
St. Thomas More [was a man of] a strong and courageous spirit, [and] like [Saint] John Fisher, when he saw that the doctrines of the Church were gravely endangered, he knew how to despise resolutely the flattery of human respect, how to resist, in accordance with his duty, the supreme head of the State when there was question of things commanded by God and the Church, and how to renounce with dignity the high office with which he was invested. It was for these motives that he too was imprisoned, nor could the tears of his wife and children make him swerve from the path of truth and virtue.
In [his] terrible hour of trial he raised his eyes to heaven, and proved himself a bright example of Christian fortitude. Thus it was that he who not many years before had written a work emphasizing the duty of Catholics to defend their faith even at the cost of their lives, was seen to walk cheerful and confident from his prison to death, and thence to take his flight to the joys of eternal beatitude.


1. cf. Pius XI | Vatican.

Endnote:

St. Thomas More was a remarkable man, loving husband and good father and father-in-law.

Several Heads of State and of Government, numerous political figures, and some Episcopal Conferences and individual Bishops asked Pope St. John Paul II [the Great] to proclaim Saint Thomas More the Patron of Statesmen and Politicians. Those supporting the petition included people from different political, cultural and religious allegiances, and the Pope took this as a sign of the deep and widespread interest in the thought and activity of this outstanding Statesman. - Source: Supremacy and Survival: The English Reformation: Pope John Paul II and St. Thomas More, Tuesday, April 19, 2011.



Further reading:


St. Thomas More | New Advent.
Motu Proprio Proclaiming Saint Thomas More Patron of Statesmen and Politicians, 31 October 2000 | Pope St. John Paul II [the Great].