I believe and think that I have found the solution.
The victory of the celestial Jesus on the spiritual archons of this age should be very rapid: Jesus wins in the same fatidic instant he is crucified.
Therefore his enemies should be defeated rapidly and rapidly replaced with the ''new archons of the new age''.
Who are the new archons of the new age ?
Assuming that they will be the same ''brothers of the Lord'', the same baptized Christians, i.e. the real members of the future cosmic family of Christ...
...and assuming that Mark expected the real conversion to Christ of all the world then known: the Roman Empire...
...then the esoteric message is: the new archons of the new age will be the Romans themselves, when they will realize that ''really this man was the Son of God!'' (Mark 15:39) : an event that not coincidentially happened just under the cross!
1) The centurion did recognize the true identity of the crucified Christ.
2) the centurion becomes Christian in that same instant.
3) eo ipso the centurion becomes allegorically ''the new archon of the new age''.
This says us that Mark is writing his Gospel in a time where the Christians of the his community are all Gentiles or quasi, and looking forward with great optimism to the conquest of the entire Gentile world.
Now we can see the join between the heavenly myth and the earthly story of Jesus: who - for the outsiders - seemed the old archons of this age - the Romans - are really the new archons of this age - for the insiders.
It is in virtue of this fact that the demons in Mark already recognize the true identity of Jesus: they are already defeated when the story is written. Therefore no need of being still in ignorance.