Some things mythicists point to is the lack of detail about Jesus in Paul, and Mark as allegorical literature. This, though, needs to be qualified in a way that favors historicity, not mythicism. Paul says he resolved to know nothing among you but Christ and him crucified (1 Cor 2:2), which suggest Paul knew far more details than he said but omitted them because of apocalyptic urgency. In the same way, the gospels indicate this selective process of choosing details, which while this problematizes the quest for the historical Jesus since much has been omitted, it does lend weight to the idea that the writers did have sources about Jesus and weren’t just inventing out of whole cloth. Yes, there was mythmaking like haggadic midrash (and mimesis), but this technique at the time was done to historical figures like the Teacher of Righteousness by the Dead Sea Scrolls writers. Regarding the selectivity of the writing process, Goodacre notes:

The reminder about absent data is constantly present in the earliest materials themselves. One of our best and earliest data sets for the historical Jesus, the surviving epistles of Paul, are explicitly selective in the information they provide about Jesus. While Paul is able to provide a relevant saying of Jesus about divorce and remarriage (1 Cor 7:10–11), he has nothing relevant from Jesus on divorce of unbelieving spouses, and he has to offer his own advice (7:12–16). Mark’s Gospel is similarly clear about its own selective nature. At his arrest, Jesus says, “Day after day I was with you in the temple teaching, and you did not arrest me” (Mark 14:49), but only a selection of those multiple days of teaching is provided by Mark. And this coheres with a related element in Mark, where the narrator presents Jesus’s teaching as something extracted from a larger mass of material: Mark 4:2: He began to teach them many things in parables, and in his teaching he said to them … Mark 4:33: With many such parables he spoke the word to them as they were able to hear it.6 The same point could be made from non-Markan material in Matthew and Luke, which presupposes extensive activities that are not narrated in either gospel, perhaps most obviously Jesus’s woes on the unrepentant cities: Matt 11:21 // Luke 10:13: “Woe to you, Chorazin! Woe to you, Bethsaida! For if the deeds of power done in you had been done in Tyre and Sidon, they would have repented long ago in sackcloth and ashes.” What happened in Chorazin? We have no idea. There is little enough written about Bethsaida—only the healing of a blind man, which is omitted by Matthew and Luke (Mark 8:22–26), and Luke’s problematic resetting of the feeding of the five thousand (Luke 9:10–17). The Synoptics repeatedly mention multiple healings, but they give only a handful of examples.7 In other words, all three Synoptic evangelists give the impression of being self-consciously selective. The narrator in Luke seems particularly keen to depict incidents as examples and illustrations from among many that he could have chosen. Although Luke gives some chronological indicators (e.g., 9:28: hōsei hēmerai oktō, “about eight days”), more often he avoids threading stories together as if they happened one after another in sequence, as Bultmann pointed out. Nor is the situation any different if we turn to the Gospels of John or Thomas. The latter famously provides no kind of connective or chronological markers, and its literary conceit is that of a collection of sayings that is highly and purposely selective. Similarly, John clearly indicates that the Gospel gives just a few representative incidents, “signs” that are chosen for their theological potential. And if the reader were in any doubt, the last verse of the gospel shines a light on the data that are not included: John 21.25: But there are also many other things that Jesus did; if every one of them were written down, I suppose that the world itself could not contain the books that would be written. Goodacre, Mark. Missing Pieces in Crossley, James; Keith, Chris. The Next Quest for the Historical Jesus (pp. 185-295). Wm. B. Eerdmans Publishing Co.. Kindle Edition (2024).