Why would Martin Luther support the Reformation?

It was the actions of Martin Luther, namely his public criticism of the Church practice of selling indulgences, that sparked the Protestant Reformation. So perhaps we should address Luther's criticisms of the Church and why he supported the reforms that would eventually explode into the Protestant Reformation. 

As a clergyman and a professor of divinity, Luther became convinced through his reading of the Bible that justification, or salvation, could only be based on faith. No...

It was the actions of Martin Luther, namely his public criticism of the Church practice of selling indulgences, that sparked the Protestant Reformation. So perhaps we should address Luther's criticisms of the Church and why he supported the reforms that would eventually explode into the Protestant Reformation. 

As a clergyman and a professor of divinity, Luther became convinced through his reading of the Bible that justification, or salvation, could only be based on faith. No amount of good works, including receiving the sacraments of the Church, could guarantee one's salvation. This was an idea that had been professed by prominent theologians before, notably Jan Hus (who was burned at the stake) in Bohemia. But Luther's criticism was more trenchant, attacking the sale of indulgences by greedy church representatives as emblematic of an abandonment of proper practices by the Church. His 95 theses, published in 1517, raised this point, and many others in a broad-ranging critique. Luther's criticisms found an eager audience in the German states, many of which were lead by princes and nobles eager to assert their independence from the Holy Roman Emperor and thus the Pope. The important point here is that Luther's emphasis on the importance of Scriptural authority in Church practice would become the foundation of the Protestant churches that formed in the wake of the Reformation. Luther's many other reforms, which included an end to celibacy by church officials (he himself married), the emphasis on a community of believers, and on lay literacy, all stemmed, in Luther's mind, from Scriptural authority, the only source for correct doctrine.