Why are there fewer books in the Protestant Bible?

Answer 1

When the early Christians were determining what books of the Old Testament should be regarded as sacred, they were uncertain as to which ones the Jews had included in their canon, there being little in the way of cordial communication between Jews and Christians. The Christian Church therefore relied on the Septuagint (LXX) as its main authority on the matter, since the LXX was an early Greek translation of Hebrew religious books.

It is believed that the Hebrew canon was established at the Council of Jamnia in 96 CE. Several of the Septuagint books were omitted and some others had material removed, that the Jews recognised as not original to those books.

After the Protestant Reformation, the Protestants decided to revise the Old Testament canon in line with the Jewish canon, although the other works were still considered worthy of study. Indeed, the first edition of the King James Bible did include the deleted books, now known as the Apocrypha (Hidden books). The Catholic Church retains the books, but considers them as Deuterocanonical. The Orthodox Churches also have a history of including a similar, but slightly different set of books as the Catholic Church.