Here is something from St. John Chrysostom ( c. 349–407), who served as bishop of Constantinople, regarding the Gospel writers, why we have only four accounts from twelve apostles, and why four accounts are plenty to confirm the truth of Jesus' words and works:
“And why can it have been, that when there were so many disciples, two write only from among the apostles, and two from among their followers? (For one that was a disciple of Paul, and another of Peter, together with Matthew and John, wrote the Gospels.) It was because they did nothing for vainglory, but all things for use.
“'What then? Was not one evangelist sufficient to tell all?' One indeed was sufficient; but if there be four that write, not at the same times, nor in the same places, neither after having met together, and conversed one with another, and then they speak all things as it were out of one mouth, this becomes a very great demonstration of the truth.” (St. John Chrysostom, pp 2-3, Homilies on the Gospel according to St. Matthew; Homily 1, part 5)