How did the Catholic Bible get seven extra books?

Answer 1

The seven books to which you are referring are from the Septuagint, which was the Greek translation of The Bible that was in common use while Our Blessed Lord was preaching and teaching. Most of the Bible references in the New Testament are taken from the Septuagint. This is the Bible that the Church accepted and was translated into Latin for use by the worldwide Church. They are considered "extra" books now only by people raised in a protestant background as those who revolted against the Church in the sixteenth century rejected them due to their support of Christian teachings.

Answer 2

The split between Christianity and Judaism occurred before the Jews had decided on which scriptures would form the canon of the Hebrew Bible. Being unable to seek advice from the Jews, the early Christian Church, which eventually split into Roman Catholic and Orthodox Churches, adopted the Hebrew scriptures that were believed most likely to be inspired works. Independently, the Jewish scribes discarded the seven books on the grounds that they were not considered inspired.

Most Protestant Churches eventually discarded from their Old Testament the books that were not included in the Hebrew Bible. They also discarded material such as the Additions to Esther, on the same grounds.