David Trobisch reminds us in The First Edition of the New Testament that the books of the New Testament canon have been arranged in way that conveys its own message to readers. So editors responsible for the arrangement of the books send a message to readers. This is part of what Trobisch explains is “the editorial concept”.
So we open the New Testament and the first book we see is the Gospel of Matthew. Now the author’s name is nowhere found in the book itself. Someone has added the title and author heading to it. So who is this Matthew? We read the book and see Matthew is one of the Twelve Disciples. So the reader is led to understand that this first book is written by one of the Twelve who were with Jesus.
Next comes the Gospel of Mark, and the reader is left curious as to Mark’s identity. But the editor has collated other books and perhaps even added the odd “incidental” line that leads the reader to learn who he is, too. I’ll return to this later.
Then we read The Gospel of Luke. This work begins with a claim that leads readers to understand many others had attempted to write gospels before this one. The reader has already turned the pages of two of these. Now this Gospel is tied by the preambles to the Book of Acts that soon follows. Now Acts concludes suddenly with an imprisoned Paul preaching in Rome and waiting trial. The reader was expecting to read about the death of Paul. Moreover, some passages in Acts are written in the first person. It is natural, then, for the reader to conclude that Acts was written prior to the death of Paul.
And if Acts was written in the life-time of Paul, then so must have been the Gospel of Luke that precedes Acts. Yet the reader has seen that Luke follows earlier gospels still, such as Matthew and Mark. It is natural, then, for the reader to view these first three gospels as all being composed very early and during the life-time of Paul and other apostles.