Historically, violating that oath could easily be punished by death. It's true that in practice, many feudal lords served themselves first, but they had to at least maintain the appearance of acting in service to the crown.
Weeeeeeeell... The sheer amount of rebellions that ended with reconciliation instead of death penalty is
so damn high that it makes the law, as you say later, just a game of pretend.
Feudalism made, effectively, every lord a
state in himself (or herself). The lord makes laws, the lord administers justice, the lord raises taxes, the lord has a monopoly on violence, the lord was recognised by other lords and engaged in diplomacy with them to advance his own interests... which is what we today classify as a state. The king (even if he was, in theory, the summit of the loyalty pyramid) had the ultimate authority, but this was in fact a useful fiction, a unifying protector in times of foreign invasion. It was true wheh the king was charismatic, strong and had the support of most nobles. When he didn't, his power dissolved, and, best case scenario, he ruled his own demesne at most (Philip I of France). Worst case, Richard II of England). As the oaths of Aragon stated, the King was as important as any other noble, and together, the nobility was greater than the king himself.
In short, when you swear fealty to a king, you act in his name, not your own. That's the essence of feudalism, and that's why the castle isn't yours, no matter how hard you fought for it. Your reward is glory and renown, which will eventually let your king know that you're indispensable and will earn you a seat at the table when lands are doled out.
Yes, but as we've seen in many of the different wars of conquest, after a war there's a period in wich the ruler gives what's been taken to his worthy followers in the war. Not giving a specific house a town they took was usually something to avoid. The two examples I know best, the Repartiments of Valencia and Mallorca by king James of Aragon, are mostly whast you'd expect: the Urrea took this castle, the Urrea got this castle. The Montcada took that one, they keep it. Very few times did the king not give a castle to someone who took a stake in its taking. The big towns were left usually under the King's protection, though.
You may see the way the game works as reasonable and fair; I say that, if the game's humans are humans like us, the political systems in Sturgia or other places with greedy lords would
not last. Raganvad is the picture of a bad king according to all Medieval traditions. I love it, and ideally, Raganvad would be facing rebellions
left and right. Fishy arrival to power, suspicion of having killed the previous monarch, greedy, foul-tempered... I'm surprised he lasted that long. Who supports him? His Nord mercenaries?
I would actually add a new sort of town in Bannerlord; big towns. Places like Pravend, Lycaron, Varcheg or Ortysia should be bigger than other towns.
Still, I don't know why my relationship with Rhagaea whent from +10 to -100 in a couple of months...