...and someone else couldn't have written them and put Matthew and John's names on them? Especially back then when we had far fewer methods to verify whether the credited author was the real one?
As for Luke slipping into first person, I've read plenty of novels and short stories written in first person--does that mean that the author is relating personal events?
What would be the motive for someone to make up such a story. And if the stories were not made up, then how come there were Christians from before the time the Gospels were written?
a) What's the motive for anyone to write any work of fiction?
b) Maybe because there were other Gospels than the four that made it into the Bible?
a) Most writers of fiction market it as fiction not as the Word of God.
b) Those other gospels were declared non canonical forgeries.
a) So the Bible is just being marketed as the Word of God? I mean, there's other texts out there that claim to be the "Word of God" (or a god, anyway), a good number of which predate the Bible, and those that postdate it could say that they're refinements of the Bible... so how am I supposed to decide between them when they all make incredible (as in, lacking credibility), absurd, ridiculous claims?
b) By whom? A bunch of guys in a room deciding which ones best fit the doctrine they wanted to push, not actual historians scrutinizing all the evidence and determining which accounts most closely match it (and we know they can't all match what actually happened, even given all the supernatural stuff, since they all contradict each other). Probably the closest we've ever gotten to a true account of Jesus' life (assuming such existed) is the Jefferson Bible, and it's not like that was particularly great, either.
A) The other texts that claim to be the word of God or a god were founded by cult leaders such as Joseph Smith who used the texts to found cults. Christianity was not founded as a cult, because in it’s early years, there were numerous Bishops all around the Roman Empire, not a single leader though the Bishop of Rome had primacy as the first among equals.
B) It was done at the Council of Nicaea by a bunch of Bishops throughout the Roman world. They evaluated the texts, and determined which ones best matched the story and teachings of Jesus Christ. As for the minor contradictions in the books, that was because of human error. That does not change the fact that they all documented the true story of Jesus Christ.