“ It was passed down to Catholics through Sacred Tradition before Scriptures were written
Yet never in writing before 100 ad... not in scripture, secular writings, contemporary art, etc.
Peculiar, if it were true.
And, most scholars, theological and secular pretty much agree that the NT in its entirety was written and likely widely disseminated by 100 AD or so. There are some 10000 copies and fragments of copies in hand today. More than any other important writing from antiquity, to include OT, Plato etc.