try to play as someone in that theatre and actually be successful there. In my previous game I started as Duke of Brittany and had to work hard to keep normans(who constantly tried to claim my lands), norwegians(who won England) and french at bay. I won the crusade for Andalusia, and had to keep muslims at bay as well.
Through the conspiracy, marriages and outright war I made my kin to be :
King of France,
King Of Navarra, Galicia, Castille
Duke of Portucale,
Duke of York,
Duke of Moray,
France got half of Aragon, and I inherited south of England (Bedford, Norfolk, Oxford, Somerset and one other duchy)
Other then that everyone is more or less in their own borders.(well, Norway collapsed and is now a bunch of independent duchies, while king of Norway owns something around archangelsk :-/ and also Poland got conquered by Hungary)
What I am trying to say here is that historical reconquista in Spain was more a miracle(political, diplomatical and military) then an inevitable event.
And if the rightful Jimena cannot set iberia to rights - why should french not intervene? why should not germans get a few early colonies in afrika?