500 years ago Martin Luther had all the traditions and pedigree. Everything was all figured out for him, but he was still racked with guilt at being incapable of working out his salvation and presenting such a putrid offering to God when he came to Him.
It was only when he stripped this away and read God's Word was he able to see what had been hidden under years of corrosion and corruption - God's unmerited grace that is bestowed unto sinners.
Luther didn't have it all figured out for him though. There were reformers working within the Church also. Luther is just remembered more among Protestants
It's too simplistic to look at it from an I believe xxx you believe yyy. xxx and yyy are contradictory therefore one must be wrong.
Take the Eucharist for example and ask the question "Is it the body and blood of Christ?"
Now, if we were to undertake answering such a question. All the Logic and all the Scripture etc. We could prove I am right. However, we could also prove you are right.
Who decides?
For the Orthodox/Catholic, it is the appeal to the Church and its tradition that decides the matter. It's just that easy.
For the Protestant, it is left to endless back and forth Even for Luther vs later interpretations. Calvin and his belief in the ever virginity of Mary are another example.
Two right conclusions from the same dataset. I can make an "ironclad" case for it from just scripture, just as you can make an "ironclad" case for it.
However, the year is now 150 AD. Prove it from your bible.
The year is no 60 AD. Prove it from your bible.