I think I've seen a similar thing myself. Not sure it was a normal campaign, or an XL one, but I know I've been playing for a while and building up a nice empire, then noticed there's not really much happening, then uncovered the map and looked around and realised there aren't any decent rival foes left - which was a major disappointment. If one faction doesn't build itself a strong position and there's just constant wars, then entire regions just get reduced back to the dark ages as all the infrastructure is destroyed. I think I just abandoned the campaign.

One thing you can do though if you're using the -ian switch, is to change control to another faction and let the AI take control of your much superior empire whilst you try transform your lowly new nation to something resembling greatness.