How come the gospels tell so many different stories and in different ways?

I'm not saying they should all be identical but if you asked 4 people who really cared about and studied, say, John F Kennedy, who lived until about 40-50 years ago or so like the time between Jesus' death and the gospels, they would at least include the same episodes (the Naval career, the family connections, the campaign against Nixon, the ination, and so on) and they'd all agree that he was a politician, that he was president and that he was shot. The gospels don't even agree on that much.