If you read my post again, I said that the canon was defined at Trent. It was declared by Pope Damasus but not definitive until Trent. Secondly, what Jerome, John of Damascus, Walafrid, etc. thought is all good and well, but they never enjoyed infallibility. Neither did Aquinas, who questioned the belief of the Immaculate Conception. Once Luther removed the problematic Apocryphal books, it became necessary to render final, binding definition of the canon. The declaration of the Magisterium is infallible - the opinions of even the greatest doctors are prone to error.
Luther's motive in removing the Apocryphal books was to render impotent the belief in Purgatory. The debate among Church doctors regarding the Apocrypha was of scholarly import, not a mission to refute dogma.
And what was declared by Pope Damasus was in part rejected by Trent.
Once Luther removed the problematic Apocryphal books, it became necessary to render final, binding definition of the canon.
It wasn't just Luther who "removed" the problematic Apocryphal. The historical evidence given by the R.C. scholar Cardinal Catejan (Luther's adversary in other matters) along with other substantial historical evidence from sources such as the The Glossa Ordinaria indicates that the general practice of the Western church from the time of Jerome until the Reformation was to follow the distinctions of Jermone, Rufinus and Athanasius regarding the ecclesiastical and canonical books.
Cordially,