The set includes Tobit, Judith, Wisdom, Sirach, Baruch, the two books of Maccabees and the additions to Daniel and Esther, with further books received in some Orthodox churches and not in others. They stood in the Greek scriptures used by early Christians and passed into the Latin Bible, so the Christian tradition inherited them as part of its scripture without a decision ever being taken to include them. The disagreement that follows is old.
Jerome, translating from Hebrew, held that books outside the Hebrew collection had a lesser status and said so in his prefaces, while Augustine treated the wider set as scripture, and the Latin church went on using Jerome's translation with Augustine's canon. That unresolved tension sat inside Western Christianity for a thousand years. It was forced open at the Reformation.
The Reformers appealed to the Hebrew collection and removed the disputed books from the canon proper, retaining them in a separate section, and the Council of Trent responded by defining the Catholic canon to include them and attaching an anathema to the denial. What had been an unsettled inheritance carried for a millennium became a confessional boundary within a generation. The books themselves did not change. What changed was that the question of who held the authority to settle their status now had to be answered.