I am not a Christian, but I was at one time. In a lot of my recent studying, it seems like everything prior to Salomon is a Hebrew origin story akin to a marvel movie. There is no evidence of any Canaanite or Hebrew slaves in Egypt.
Egypt is still hiding what's under the Spinx, so maybe the evidence is kept hidden .. except that the kingdoms of Israeli shared time in existence alongside Egypt.
People retroactively cannon things into history the same way writers retcon movies. People believe in the prophecies because they can be mapped onto history. If another group's history had survived, we'd map modern events onto their fantasy. People would believe in Gilgamesh instead of Adam and Eve.
Most Christians today (evangelical, reformed, doesn't matter) would not recognize the Christianity of 200 AD.
If a world changing event happens (or made to happen) some will believe .. if it does not happen, they will say "no one knows the hour or day.." ... vague prophecies help continue the story
"Truly I tell you, some who are standing here will not taste death before they see the Son of Man coming in his kingdom."
The reformed will say Matthew 16:28 is symbolic. The literalists will say someone from that time is somehow still alive today and will be a herald (like the "Wandering Jew" myth). If the religion, and the wold, survives another iteration, either it will be dismissed or filled in, with a real person or a fictions one, with a natural or supernatural explanation.
All this has happened before, and all of this will happen again.