He does not say that anywhere in that passage.

For a detailed debate over this kind of thing see my whole series with Jonathan Sheffield on the Long Ending of Mark.

“Come now, you who would indulge a better curiosity, if you would apply it to the business of your salvation, run through the apostolic churches, in which the very thrones of the apostles are still pre-eminent in their places, in which their own authentic writings [ipsae authenticae litterae eorum] are read, uttering the voice and representing the face of each of them severally. Achaia is very near you, (in which) you find Corinth. Since you are not far from Macedonia, you have Philippi; (and there too) you have the Thessalonians. Since you are able to cross to Asia, you get Ephesus. Since, moreover, you are close upon Italy, you have Rome, from which there comes even into our own hands the very authority of apostles themselves.”** (Adversus Marcionem 4.5.1–2)

There isn’t any evidence bibliomancy was a thing then. It appears to be a later development, and thus resulted from the codex trend, rather than causing it.

But your other premise stands, for instance Homeromancy (which appears to have slightly predated and possibly inspired Bibliomancy) did have the same effect in popularizing the codex.

It occurs to me that the codex form provides another advantage, too, which is bibliomancy. It’s hard to select a verse genuinely at random if you are having to continually wind/unwind a scroll. But a codex can be rapidly thumbed or flicked, and then opened at a random page to see what verse will jump out at you. Bibliomancy becomes possible.

So, this could have been another factor behind the quick spread of C150. When churches said “why do we have to dump our old scrolls and replace it with your codex?” the response would be “well one reason is because you can use it as a divine oracle! And you can’t do that with those scrolls.”

http://trobisch.com/david/wb/media/articles/20071226%20FreeInquiry%20Who%20Published%20Christian%20Bible%20BW.pdf

Read OHJ to understand why the scenario you imagine can only achieve at best a 1 in 3 chance of being true on extant evidence. And read my article on transition theory as to why your scenario can never be known to be true due to the near complete destruction of evidence needed to test it by.

Going backwards, I can assemble:
C150: Four Gospels, written prior between 70 and 100 by four different people, in up to four different places, all starting with Mark, then Matthew, then Luke and finally John, no Q, M, nor L. Mark historicized a messianic space angel envisioned by Paul and described in some admonitory mail Paul sent to some places which might be named in the letters as received, probably in the 50s.

Now from here back it’s getting murky. Between around 30 and around 50, something. Paul does not seem to have “invented” Christianity, since the churches to whom he dispatches his mail are implied to have already been going for long enough to develop schisms from an original already in-place theology, and 1 Corinthians 15:9, which is currently judged authentic Paul, confesses his prior persecution of the church. Unless that is an interpolation to harmonize with Acts, as Robert Price once argued, in which case there is only an historical James and Cephas as “Christians before Paul” who are regarded by those destination churches as having some prior authority to Paul. So sometime in the first third of the first century there is a thought event which I cannot find from your blogosphere.

Was there a Qumranic council of 12 initiates whose work involved extending their own messianic mythology from which the first Jesus story originated? I know we don’t know. I’m wondering what you think is most likely.

I find it difficult to resist a minimal historicity hypothesis in which a deluded cult leader, against all devoted follower expectation meets a disastrous end in Jerusalem, spawning a grief rationalization process resulting in the transmission of just-so space angel stories that became Paul’s received version. Then Mark begins the process of re-historicizing the failed messiah in Paul’s tradition after the catastrophe of 66-70, which conveniently induces a local moment of institutional dispurtion for Judaism which is also an opening for the young Jesus church. There is interesting evidence for such a process of cult follower rationalization here:

https://celsus.blog/2019/01/04/the-rationalization-hypothesis-is-a-vision-of-jesus-necessary-for-the-rise-of-the-resurrection-belief/#more-17140

James Tabor, whom I am aware you hold a declining opinion of due to the Talpiot episode, believes something similar based in large part on his work related to the Branch Davidians. His proposed reactions to failed messiahs is nearly identical to those described in case study in the Celsus blog article: extend the prophetic deadline to infinity, or allegorize the prophecy. The allegory that Paul transmits has little more power to convert than other mystical cults, so the process of re-historicization begins with the intended effect of grounding the myth in relatably human yet also miraculous clothing, which also begins the process of extending the deadline to infinity and allegorizing the prophecy ever more. That Mark invented new Christology problems for future theologians by orders of magnitude by doing so has been amply demonstrated to have made no difference to the credulous. Mark’s innovation of linking the Jesus character to John the Baptist has the ring of narrative technique – it is a lacuna in your otherwise thorough deconstruction of Josephus that the John the Baptist reference has escaped scrutiny as authentic. If it is, Mark’s move is clever – if there was a living but vague memory of the Baptist, it is easier to imagine a relatively forgotten historical figure as his successor. “But verily I say unto you – Elvis had a protege who was the young Anointed One who was also called Buddy Holly!” (They didn’t care about accurate chronology, so neither does my analogy). Now if the Anointed One cult has been spreading Space Angel beliefs about him, I have a historical figure to pin the Space Angel on. “Now Buddy came to Elvis in Memphis while Elvis baptized in the liquors of Beale Street and Elvis said I am not worthy to don His spectacles…..” None of this need ever happened. But the living memory of the one and the historical existence of the other hook the attention of the convert.

It is a satisfying explanation for an origin, and it leaves non-zero the possibility of future archeological evidence. Though slim, non-zero. It’s not nothing, in other words.

What is the originating thought event I am missing in your mythicist construction?

Thanks! 🙂

Good catch! Thank you for pointing that out. The YouTube link is here. I’m fixing the article as well.