One might consider, with some radical critics, whether the relationship "From Paul to Marcion" should not be reversed. In that case, Marcion would not be a pupil of Paul, but the figure of "Paul" would in reality be a creation of Marcionism, by means of which the Marcionites retrojected their theology into the apostolic past, in order to provide themselves with a pedigree and a precedent for their doctrines in the theological conflicts of the second century.
And indeed, there were besides Van Manen radical critics who reacted to the question in the sense just mentioned. One of them was the Dutch classicist S. A. Naber, who in his "Nuculae," written in Latin, came to the result that the Pauline Epistles "ortas esse in Cerdonis vel Marcionitarum scholis" ("arose in the schools of Cerdo or Marcion").
https://depts.drew.edu/jhc/detering.html
This supposes that the "apostolic past" was already known (for his importance) by the time the epistles were fabricated by cerdonites/marcionites. It seems that the fabricated Paul assumes by construction a date that is
already fixed:
the apostolic past.
Who invented the "apostolic past"?
Who invented the tradition of the Pillars?
The fundative text of the tradition of the Pillars: was it a first gospel? Hardly so.
Was it a text as lost Acts of Apostle
X, Acts of Apostle
Y, Acts of Apostle
Z?
Those lost Acts (by Jewish-Christians) would have founded the "apostolic past" hence creating consequently the need (for cerdonites/marcionites) of lost Acts of Paul
before, and of Epistles of Paul
after.
Still no "Acts of Jesus" (a first gospel) in the horizon.
Then the
Acts of Pilate were written: something as the preaching of Christ by Pilate in Rome.
Then Pilate was chosen as judge of Jesus: the first gospel.
CONCLUSION:
The Acts of the Apostle
X, Y, Z, etc
preceded the first gospel (="Acts of Jesus") and caused the need of one.