the question arises naturally: why the demons would tell the truth? Demons should tell always a lie, by definition.And devils also came out of many, crying out, and saying,
Thou art the Son of God.
My suspect is that the devils are insinuating the exact (false) suspect that the disciples of Jesus, Peter, and even the enemies of Jesus have more and more. Namely, that Jesus is the Jewish Christ, the Son of creator God.
See the sequence of events:
1) Pilate found no evil in Jesus.
2) The Jews (remember: enemies of Pilate, by definition), want that Pilate put Jesus to death.
3) The Jews put on Jesus' mouth the messianic claim because they desire ardently that Jesus reveals his power in extremis (destroying so Pilate himself!). (for them, any attempt to kill Jesus would be as any attempt to kill the Incredible Hulk, IF Jesus was really the Christ.)
4) The son of man is killed but no fulfillment of messianic prophecy happens and on the contrary Pilate remains in his place: instead, the destruction of Jerusalem is reflected on the cross. Jesus is NOT the Christ, is NOT the Son of YHWH.
Question: if for you all this is only horrid & fanciful interpretation, you would not have the desire to write a gospel in order to convince you (and others) that Jesus IS truly the Christ, he is really the son of YHWH?