Under that basis I assume that the documents are historically reliable and each historical claim should be granted as true unless good positive reasons are given to the contrary.
1) The gospels are not "historical claims", Mark is a myth. It is not written as history in any way shape or form. It IS written as a myth. No sources, explanations for unusual events, (Pontius Pilate, would let a violent and murderous rebel go free,and no ceremony is ever attested as having taken place), improbable events, borrowing from OT narratives, Psalms, 20 close parallels to Romulus and the RR hero myth, all found in Greek myth. Greek theology - savior demigods, salvation, baptism, eucharist, Logos, a devil, afterlife, layers of parables, ring structure and more literary devices. No religion is a historical claim. No mystery religion is a historical claim.
Myth from that time does use real people and places:
"So we already have a bit of contemporary background information showing us that fictional biographies were commonplace at the time, and thus warrant caution when examining writings that may look like histories upon first glance. However, there are also certain things we should expect to find in writings that are laden with myth and allegory as opposed to history. We can’t simply try to categorize the writings as fitting within some particular genre, as myths have been written in any and all genres, even as historical biographies (as was just mentioned), for example Plutarch’s
Life of Romulus. In fact, quite a large amount of ancient biography, even of real people, was composed of myth and fiction, and thus we are forced to actually examine the content in detail to determine whether or not it is more likely to be myth or history. Some characteristics of myth include (but are not necessarily limited to): potent and meaningful emulation of previous myths, or potent emulation of real events in some cases; the presence of historical improbabilities — which is not only limited to magic or miracles, but also natural events and human behaviors that are unrealistic as well as the presence of amazing coincidences; and also the absence of external corroboration of key (rather than peripheral) elements, since a myth often incorporates some real historical people and places that surround a central mythical character and story (just as we see in most fiction, e.g., though Dorothy’s home-state of Kansas is a real place, the primary setting, main characters, and story in The Wizard of Oz, including the Wizard of Oz himself, are fictional constructs). It should be noted that not all of these characteristics need be present simultaneously for a story to be myth, but the more that are, or the more instances of each type found, only increases the likelihood that what one is reading is in fact myth rather than history."
Historical claims don't re-write the Elisha story from Kings 2, use Psalms verbatim, and many other stories. The triadic ring structure and many other devices are not how history is written.
Look at the parallels just from Jesus Ben Ananias:
1 – Both are named Jesus. (Mark 14.2 = JW 6.301)
2 – Both come to Jerusalem during a major religious festival. (
Mark 11.15-17 =
JW 6.301)
3 -Both entered the temple area to rant against the temple. (
Mark 14.2 =
JW 6.301)
4 – During which both quote the same chapter of Jeremiah. (Jer. 7.11 in
Mk, Jer. 7.34 in
JW)
5 – Both then preach daily in the temple. (
Mark 14.49 =
JW 6.306)
6 – Both declared “woe” unto Judea or the Jews. (
Mark 13.17 =
JW 6.304, 306, 309)
7 – Both predict the temple will be destroyed. (
Mark 13.2 =
JW 6.300, 309)
8 – Both are for this reason arrested by the Jews. (
Mark 14.43 =
JW 6.302)
9 – Both are accused of speaking against the temple. (
Mark 14.58 =
JW 6.302)
10 – Neither makes any defense of himself against the charges. (
Mark 14.60 =
JW 6.302)
11 – Both are beaten by the Jews. (
Mark 14.65 =
JW 6.302)
12 – Then both are taken to the Roman governor. (Pilate in
Mark 15.1 = Albinus in
JW 6.302)
13 – Both are interrogated by the Roman governor. (
Mark 15.2-4 =
JW 6.305)
14 – During which both are asked to identify themselves. (
Mark 15.2 =
JW 6.305)
15 – And yet again neither says anything in his defense. (
Mark 15.3-5 =
JW 6.305)
16 – Both are then beaten by the Romans. (
Mark 15.15 =
JW 6.304)
17 – In both cases the Roman governor decides he should release him. (Mark 14.2 = JW 6.301)
18 – But doesn’t (
Mark)…but does (
JW) — (
Mark 15.6-15 =
JW 6.305)
19 – Both are finally killed by the Romans: in
Mark, by execution; in the
JW, by artillery. (
Mark 15.34 =
JW 6.308-9)
20 – Both utter a lament for themselves immediately before they die. (
Mark 15.34 =
JW 6.309)
21 – Both die with a loud cry. (
Mark 15.37 =
JW 6.309)
The odds of these coincidences arising by chance is quite small to say the least, so it appears Mark used this Jesus as a model for his own to serve some particular literary or theological purpose. In any case, we can see that Mark is writing fiction here, through and through.
2) positive reasons, although not needed, are right there, you just ignore them. The story is a trending theology/mythology happening in Greek occupied nations. Paul even says the first Christians are found in Antioch. History shows this was the center of Hellenism and it's the "cradle of Christianity". The name "Christian" is from Antioch.