Again, there wasn’t an apostolic canon.
By the time Marcion came on the scene, the entire bible had been preached to countless people in the known world...
God said he'd preserve his words...I don't see anywhere in the scriptures where Jesus told the apostles and desciples, 'Good luck figuring all this out'...And I didn't see where Jesus told anyone they would be leaderless in knowing what to teach and preach for a few hundred years when the Catholic religion would figure it out for him and let them know...