Remember that the Reformers set out to reform all of Christendom; that they ended up with countless minor factions bickering amongst themselves and against Catholicism and Eastern/Oriental Orthodoxy means that the Reformation was, at least to an extent and despite many notable successes, a failure.
I. Christendom Understood Core [Capital-T] Truths Before the Reformation
Prior to the Reformation, there was a relatively stable notion of what Christianity looks like: Catholicism in the West, Orthodoxy in the East, Oriental Orthodoxy in parts of Southern Asia – these were similar enough creatures that a traveller would feel comfortable wandering into a Divine Liturgy, Mass, or Holy Qurbana and (other than obvious linguistic issues) have at least a rough idea of what was going on. Introductory prayers, readings, homily, and the Eucharist, with the Our Father thrown in there somewhere, and perhaps a Sign or Kiss of Peace. The belief systems were largely the same, and many of the issues in dispute were likely meaningless to the average believer: how many people can really get that worked up over whether the Holy Spirit proceeds from the Father and the Son, or just the Father?
In the West (excluding Jewish and Muslim pockets), there were two groups of Christians: religiously fervent Catholics and religious apathetic nominal Catholics. Of course, there were strong anti-Papal sentiments throughout much of northern Europe, but this wasn’t unlike the way that many loyal Americans find Washington, D.C., distasteful. Certainly, there were people who were clueless as to why the Church believed x, and had perhaps long ago discarded that part of the Faith, but there was a clear capital-T Truth, reinforced by the countless Saints who died for the one-and-the-same Faith. Some people were better Catholics than others, but at least there was a central scale to judge all of that by.
II. The Reformation’s Counter-Truths
With the Reformation, this stability was destroyed, and suddenly, nothing was beyond question. To an extent, this was a positive: when no one questioned why Catholic Truths were true, they never learned the answers… as a result, their Faith had shallower roots, even if this was a fact unapparent to themselves or others. It’s the paradox of success – with few exceptions, only combat can produce the finest soldiers, just as with few exceptions (like Aquinas), only heresy can produce the finest apologists.
Much good came from the Reformation (and in response to it), in terms of bringing many formerly apathetic people to a real relationship to Christ, in terms of sounding a clarion call for internal reforms (resulting in the much-needed Council of Trent), and in terms of creating inspiring saints and martyrs: individuals like St. Francis De Sales, St. Edmund Campion and the English martyrs, Ss. Stephen Pongracz and Melchior Grodziecki, and so forth. But despite these many ongoing successes, the Reformation, as such, was a failure.
Martin Luther was genuinely convinced that the forcefulness of his argument for sola fide that any one who listened to the argument with an open mind and heart would accept it. That this didn’t happen caused him endless pain, and much bitterness. At the outset of the Reformation, Luther believed that the Jewish people would be converted — that they had been kept out of the Church by anti-Semitism and papal corruption and that exposed to Luther’s redisovered Gospel message, they would eagerly embrace it. When they didn’t, an embittered Luther penned the viscously anti-Semitic On the Jews and Their Lies, which reflects his understanding of his opponents:
If I had not had the experience with my papists, it would have seemed incredible to me that the earth should harbor such base people who knowingly fly in the face of open and manifest truth, that is, of God himself. For I never expected to encounter such hardened minds in any human breast, but only in that of the devil. However, I am no longer amazed by either the Turks’ or the Jews’ blindness, obduracy, and malice, since I have to witness the same thing in the most holy fathers of the church, in pope, cardinals, and bishops.
In other words, Luther found the fact that he was right so compelling that only “blindness, obduracy, and malice” could explain why Catholics, Muslims, and Jews disputed the “open and manifest truth” of sola fide Protestant Christianity — that is, that Luther’s understanding of justification was a capital-T Truth. The passage marks something of a turning point. Prior to this, Luther desired to remake Christianity as a Faith which clung to sola fide, and from his own testimony, he seemed to believe that all well-meaning Christians would join his cause once he explained himself more clearly.
But the Reformation was proving much nastier than he could have expected. Rather than two competiting visions, Catholicism v. Lutheranism, the Reformation had become Catholicism v. everyone’s individual interpretation. With the rise of the radical Reformers, the unravelling of the Reformation accelerated. Calvin and Luther disagreed mightily with one another, both despised the radicals, and many of the Protestant leaders seemed more intent on putting each others’ followers to death than creating a New Christendom. What had been, more or less, a religious civil war between East and West devolved with the Reformation to a free-for-all brawl.
The dream of sweeping away the last vestiges of “Papism,” and replacing it with a New Christianity more authentic to Her ancient roots was given up long ago. Rather than creating one unified New Christendom, Protestant leaders watched, helplessly, as minor issues divided their flocks into increasingly isolated factions. Meanwhile, it became more and more obvious on the Catholic side that unlike earlier heresies, these fires had spread too far to be contained.
In the early days of the Reformation, it looked very much like a typical revolution: one group of people rebel against those in power, and both vie for the throne. By the end, it became clear that it was more like the US Civil War, dividing one people into two.