The Protestant accounting for the Scriptures lies in God's inspiration of the Scriptures. Which is how the Jews and the early Christians were able to recognize what the Scriptures were long before groups such as the Roman Catholics and Eastern Orthodox came along. These groups, among others, claim to be the original church but all come to different conclusions on what the canon of Scripture should be, revealing that they are a later sect, anachronistically imposing their standards on what God had originally revealed.
Any of these groups have a low view of the Scriptures and do not want the individual to turn to the original Biblical documents, so that they may first prejudice the individual against the Scriptures and each impose their own traditions in it's place. But wherever the Scriptures have been freely shared, Protestantism has flourished, because Protestantism does not seek to reinterpret the original documents according to it's own tradition, but understand the original documents according to their original context. Thus, it is rightly said that Protestantism is nothing more than Biblical or Apostolic Christianity.
We are being told that we should understood the 1st century text, according to one of these sects, each of which cannot trace itself until centuries after the original documents had been written.
And while God defines how the proper Church should obey the boundaries outlined in the Scriptures. Each of these sects will insist that we must understand the original documents according to their understanding.
Lastly, because the Catholic canon for Scripture does not align with the Orthodox canon of Scripture, we can see the competing anachronism of these sects, not that these are the only two sects who claim to be Apostolic, imposed onto the history of the early Church and especially the Church at it's inception, that is the Apostolic Church.
Ask yourself: did the Apostles ever say anything remotely similar to "the Church is the necessary prerequisite to Scripture?" Clearly not, and so when you are building your worldview on a different foundation than on what they have already laid, do not be surprised when it goes awry.