But seriously, do you think that, say, when the Franks sat around in recently conquered lands, they looked around and went, "Now, Joe over there is the best fighter, but not too great at counting sheep, so we'll give him a small estate, and just tell Bob, who is a good farmer and thus going to get a big plot of land, to give Joe some of his excess money." Really? I find that implausible.
Obviously, yeah, a catastrophically horrible land-manager might not be preferred (though I can think of plenty of cases where it wouldn't be crippling: I'm thinking of the Mayor of the Palace phenomenon in the late-Merovingian period particularly), but I think intentionally shifting your dukes out of combat roles...
Well, I dunno, there might be some kind of precedent, I feel like, somewhere in 1300's Italian states, maybe some German ones... but broadly it just seems very strange to me.
Yes I think such things did happen. Medieval doesn't equal stupid. There were certainly nobles that understood the value of well run estates. Really the idea of foolish nobles that squandered their holdings wealth is far more common in later ages. Powerful figures like Dukes did not need to take the field, ever. That isn't to say they never took the field. Their value wasn't necessarily in their own fighting skill, but in the men they provided to the armies. They could just as easily send a senior knight to command their levies as they could themselves.
