Dont forget that somehow in the MNB universe, in the year 1352, ghouls came to existence, and somehow the entire kingdom of Swadia had a rebellion, and formed a new faction called the Vaegirs. King harlus was revived as a skeleton and is planning on restoring his throne from the current swadian king.
Mount and blade lore is very rocky indeed, so its safe to assume Talesworlds didnt think about lore until Bannerlord popped up in Amagradon's head.