These gospels were banned by the Council of Nicaea. The First Council of Nicaea was a council of Christian bishops convened in Nicaea in Bithynia (present-day İznik in Turkey) by the Roman Emperor Constantine I in A.D. 325. The Council was the first effort to attain consensus in the church through an assembly representing all of Christendom.
Its main accomplishments were settlement of the Christological issue of the relationship of Jesus to God the Father; the construction of the first part of the Nicene Creed; settling the calculation of the date of Easter; and promulgation of early canon law.
The existence of these gospels were unknown until several fragments were discovered in modern times. Since the only long fragment is a Coptic translation, most of the original Greek text is still lost. And even the long fragment may only include about half of the book.
Because the “Mary” in this gospel is depicted as a very prominent disciple, most scholars assume that she is Mary Magdalene, although in the extant text she is always just called Mary. The gospel emphasizes her prominence by presenting her as a strong leader, and by suggesting that she was the most favored disciple of Jesus and received a special revelation from him. It also suggests that this led to a conflict with Peter, who may have seen her as a threat to his position as overall leader of the disciples in the period after Jesus departed.