The Apocryphal (Deuterocanonical) books were always part of the canon of the first Christians. This is a fact. The earliest bible manuscripts contain the apocryphal books, as do the Dead Sea Scrolls. The Jews had taken the so called "apocryphal books" out of their bibles in about the 2nd or 3rd century to make a distinction and argument with Christians that the only reason they misunderstand the OT messiah is because they have the wrong bible. The christians up until the 5th century used the Septuagint (LXX) exclusively. Jerome, who was a deceiver, introduced the Jewish version into the church through the Vulgate. The "apocrypha" was still being used because EVERY CHRISTIAN was aware that these books were in the bible.
Note: Jerome taught that the bible contained lies, and that the Apostles were liars. Jerome was financed by Jews to introduce the Hebrew text into the church, which he did. The next major change to the bible came when Gutenberg printed the bible using the Hebrew text without the Apocrypha, for he too was Jewish. Gutenberg was financed by a Jonathon Faust (of Geothe's fame - he sold his soul to the devil), which he (Faust) stole the manuscripts off Gutenberg, and Gutenberg ended up having no control over the bible that he first printed.