Jewish Christians who held to the ongoing validity of the Law used only Matthew; certain groups who argued that Jesus was not really the Christ accepted only the Gospel of Mark; Marcion and his followers accepted only (a form of ) Luke; and a group of Gnostics called the Valentinians accepted only John.
The Gnostics and Valentinians, then, are simply products of a very understandable power play in the early Christian Church between Christian Jews and Christian Gentiles. It is interesting that the non-Jewish Christianity largely won, only after the Hebrew Bible was accepted as an Old Testament.
