Why did Philip II take upon himself the leadership of the Catholic Counter Reformation?

Catholic AnswerPhilip II of Spain played a large role in the Catholic Reform, and as he was King of one of the largest Catholic countries at the time, he had a big job, but he certainly did not take leadership of the entire Catholic Reform. The Popes, the Council of Trent, and innumerable saints and religious orders did that.

from Modern Catholic Dictionary by John A. Hardon, S.J. Doubleday & Co., Inc. Garden City, NY 1980

A period of Catholic revival from 1522 to about 1648, better know as the Catholic Reform. It was an effort to stem the tide of Protestantism by genuine reform within the Catholic Church. There were political movements pressured by civil rules, and ecclesiastical movements carried out by churchmen in an attempt to restore genuine Catholic life by establishing new religious orders such as the Society of Jesus and restoring old orders to their original observances, such as the Carmelites under St. Teresa of Avila (1515-98). The main factors responsible for the Counter Reformation, however, were the papacy and the council of Trent (1545-63). Among church leaders St. Charles Borromeo (1538-84), Archbishop of Milan, enforced the reforms decreed by the council, and St. Francis de Sales of Geneva (1567-1622) spent his best energies in restoring genuine Catholic doctrine and piety. Among civil rulers sponsoring the needed reform were Philip II of Spain (1527-98) and Mary Tudor (1516-58), his wife, in England. Unfortunately this aspect of the reformation led to embitterment between England and Scotland, England and Spain, Poland and Sweden, and to almost two centuries of religious wars. As a result of the Counter Reformation, the Catholic Church became stronger in her institutional structure, more dedicated to the work of evangelization, and more influential in world affairs.