Final answer:
The inclusion of the Apocrypha as canonical was primarily initiated by the Catholic Church, with the trend becoming more defined during the Council of Trent in response to the Protestant Reformation.
Step-by-step explanation:
The trend toward including the Apocrypha as canonical in Christian texts has a complex history. During the early development of Christian doctrine, there was debate about which texts should be considered authoritative. It was in the Renaissance that the Western Church, specifically the Catholic Church, under the influence of councils and the translation work of figures like Jerome, began to define more precisely which texts were canonical. The trend was effectively solidified at the Council of Trent (1545-1563), which was the Catholic Church's response to the Reformation. This council addressed issues of doctrine and included the Apocrypha within the canonical texts of the Latin Vulgate Bible.
It's important to note that different branches of Christianity have different views on the Apocrypha. The Protestant Reformation led to a rejection of these texts as canon by many Protestant traditions, while the Catholic Church maintained them as part of the Deuterocanonical books.
In summary, the inclusion of the Apocrypha as canonical was primarily initiated by the Catholic Church, which was trying to maintain unity in doctrine and respond to the differing teachings that were emerging at the time, particularly during the Reformation era.