“But there was Protestant soteriology, like in Augustine, Chrysostom, and also even in contrary views of what the Papacy is.”
No. Years ago I read Alister McGrath’s doctoral dissertation when it was published as a two volume book. https://www.amazon.com/Iustitia-Dei-Christian-Doctrine-Justification/dp/0521533899 I do not know what changes might have been made between the original two volume version and the third edition available now. In the original version he mentioned that Luther introduced a “theological novum unknown in the previous fifteen centuries of catholic thought” into soteriology. That quote is found through the “Look Inside” feature at Amazon for the book. Just type in “novum” as your search word and it should come up as the second listing but it won’t let you go to the actual page. If you put your cursor on it, you can read at least that much of the quote. Anyway, the point is, that even as great an expert on Protestant soteriology as Alister McGrath ADMITS that Luther introduced NEW THINGS, NOVELTIES into an understanding of salvation that became pervasive among the emerging group we call Protestants.
Now, I realize that’s only one thing - but it is admitted by a great authority among Protestants (oh, I can just hear the coming possible response, “We only have the Bible as out authority. . . “). If McGrath is an honest man, and admits Luther was wrong on even one small point that made its way into Protestant soteriology, what else could there be that he doesn’t realize is a “novum”?
Luther was NOT following St. Augustine. He was adapting him. Luther was NOT following St. John Chrysostom. He was adapting him as he saw fit. Luther didn’t even follow the Bible. He adapted it to suit his needs.
Some Protestants have harsher views of Luther than I do:
There were some differences, this is true, but Augustine's views were very different than what Rome was teaching during Luther's time or even today. For example, Augustine taught that only the Elect can enter into heaven, and the Elect are those who specially receive grace unto salvation, which is not based on any foreseen good works, but on God's mercy alone. Those who do not enter into heaven were either not given grace at all, or were only given a little grace, which they could use to go very far, but ultimately had to be cast out.
This is not what Rome teaches today, as they teach--and even explicitly interpret verses Augustine used in opposite ways--a sort of universalism, where God grants grace, or at least offers, grace to all people. Augustine taught the exact opposite.
I had no idea Luther said such things. Well.