Why does the Bible include three Synoptic Gospels?
The Gospels of Matthew, Mark, and Luke are called the Synoptic Gospels because they obviously draw upon common source material. John, in contrast, is less similar to any of them than they are to each other. Mark is widely considered the oldest of the three, but it isn't necessarily the ultimate source.
Why did the 4th-century Council of Rome, which compiled the Biblical Canon, include three Synoptic Gospels rather than choosing the one they considered most authoritative? Having all three creates the problem of inconsistencies among them, ranging from the wording of quotes to entire events.