One simple question. Why do you believe scripture is inspired and that God let the same people pervert oral tradition? Wouldn’t it make sense to protect both? In reality he had to since most of the writers weren’t there and there was no bible, he had to protect oral tradition
Oral tradition is not inspired and changes.
In fact, we have a video of how oral tradition has changed...
Bishops Transferring Oral Traditions Caught on Video!
This is why oral tradition is not inspired nor authoritative.
Once again your logic would require 1st century souls to have submitted to the judgments and oral tradition of the magisterial preservers/stewards of the OT, rather than following itinerant preachers whom those who sat in the seat of Moses rejected.
In addition, since as with oral tradition, the Holy Spirit inspired the writing of some Truths from pagan sources, then by your logic the totality of these must also be held as inspired.
Instead, Scripture separates the "wheat" of oral tradition from the "chaff," and with the establishment of a canon being due to the unique enduring heavenly qualities of these writings, which conciliar decisions are to affirm.
And in reality, scholarly disagreements over the canonicity (proper) of certain books continued down through the centuries and right into Trent, until it provided the first "infallible," indisputable canon - after the death of Luther.