[Agema]

According to the game, whoever doesn't win, loses.

But some people may prefer to go away with the thought "I was second" because they were they were the last player to be defeated, or may even think "I allied with X for him to win therefore I was part of a team victory".

Not stopping large and dangerous opponents is also actually realistic: the rise of Nazi Germany; the Celts not uniting to resist Caesar until he'd already pacified most of Gaul; the crusaders sacking Constantinople with the Turks approaching the gates of Europe.

I think it's true that there's a sense people want to take down a bitter opponent. There's a sense of victory in overcoming a local opponent, even if you can't overwhelm the big guy who comes after.