...as to the beginnings and conclusions of the two gospels, Klinghardt observes that the beginning of Mark seems more developed than the beginning of MLk, which seems to presume that the reader knows about Jesus; the first statement about the identity of Jesus is in the mouth of demons (MLk 4:31-37 par. Mark 1:21-28). Before this story in Mark, by contrast, Jesus receives a considerable introduction from the narrator (Mark 1:1), John (1:2-8); and the heavenly voice (1:9-11).
(Jens Schröter, Tobias Nicklas, Joseph Verheyden, Gospels and Gospel Traditions in the Second Century: Experiments in Reception, p. 146)
The fact that only demons know Jesus - and only they can inform the reader about the Jesus's identity - supports Mcn's priority over Mark, since Ignatius insists at contrary that Satan didn't know the identity of Jesus:
Ephesians 9:
Now the virginity of Mary was hidden from the prince of this world, as was also her offspring, and the death of the Lord; three mysteries of renown, which were wrought in silence by God. How, then, was He manifested to the world? A star shone forth in heaven above all the other stars, the light of which was inexpressible, while its novelty struck men with astonishment.