What was the heart of the Reformation?

Carlton McLeod explains in this video that he believes the heart of the Reformation was Sola Scriptura, "by Scripture alone." The Church, through the Middle Ages, had drifted away from the understanding that Scripture governed all of life. Traditions and customs of man superseded clear commands of Scripture.

During the Reformation, the Reformers directly opposed this idea by declaring that there is no way to please God by various man-made rituals. Accordingly, many of the doctrines that sprung from the Protestant Reformation came from the careful study of Scripture. The Reformers steadfastly declared that Scripture alone was sufficient.  

1 Thessalonians 2:13 (NKJV) – “For this reason we also thank God without ceasing, because when you received the word of God which you heard from us, you welcomed it not as the word of men, but as it is in truth, the word of God, which also effectively works in you who believe.” 

I think the heart of the Reformation was Sola Scripturum. I really believe that. I think that The church through the Middle Ages had gotten away from scripture alone as is well documented. And I think the reformers said there's no way that we can please God with man-made ideals and rituals and so forth. And so the essence of it in so many ways is the Sola Scriptura because all the doctrines that the Protestant Reformation became known for came from a careful study of the scriptures themselves.