Sola Scriptura, or Scripture Alone is the cornerstone of the Reformation as through scripture and no other is the most autthoritative source for it is the word of God in written form
The inspirational nature and power of the Bible is such that it defends itself and needs no special interpreter. The false prophets tried and treid again to destroy its authenticity and credibility with the same Satanic line:
"Hath God saith...."
They do so by claiming it has errors... it is incomprehendable ... lost in translation... corrupted by man... and so thus requires a person of such spiritual quality, being, or intelligence to properly interpret it.
In order to manipulate its meaning for his/her benefit.
Satan was the first to cast doubt on the word of God; then false prophets of various kinds arose throughout the ages to do the same but before the word was written it was a contest of miracles.
When the word was wrritten, and the Prophets no longer relevant, then new forms of attacks came into being.
The Gnostics written their own text with a claim of having exclusive answers from God to subvert attention from scripture. Muhammad claimed that the scriptures has been corrrupted in the 6th century, then Joseph Smith clamed the same in the mid 19th century, and the Jehovah's Witnesses have their Watchtowers and Awakes. In one way or another, cult leaders made themselves directly or indirectly present themselves as sole authority in interpreting scriptures by the virtue of their persona.
They all have this one thing in common: a necessity of an authority over the scriptures and the Pope is no diffferent.
According to the Roman Catholic church, while the Scriptures is inspired, the Pope alone could interpret scripture correcly. Catholic Apologists claimed that without the Pope, there will be a myriad of churches claiming this and that, so the need of an authority to decree scriptural orthodoxy.
While that is true, that only assumes that the scriptures are difficult to understand which is a classic attack on the scripture itself. "Hath God saith"?