That explains it. Pre-built settings are tough to tweak, which is why I never use them. Too many existing, sacrosanct linkages. In my games, if I need orcs somewhere, then there's gonna be orcs there. Stuff like that is just the world being built on the fly.
I really like that different regions have different mixes of races/species/heritages and cultures. I like that different areas have different challenges. When PCs travel to a region they have never been before, I want it to feel different.
So if you live near the Graywall Mountains, you might encounter orc or (more rarely) gnoll raiders. If you live near the Byeshk Mountains, the raiders are more likely to be harpies. Near the Seawall Mountains, the raiders will be goblinoids, probably hobgoblins and/or bugbears, but there are also kobolds who interfere with mining operations. The Blackcap Mountains house fiends, aberrations and really evil brigands. Raiders from the Icehorn Mountains are demon worshipping barbarian tribes, collectively referred to as the Carrion Tribes, and containing various races; plus this is the route fiends must generally follow if they want to enter the "cilvilzed" lands. The Mountainroot and Hoarfrost Mountains are home to dwarf clans and the Jhorashtar orcs; there is a web of clan alliances, with most clans having a few allies and a few enemies among the dwarf clans, while also being at war with the orcs; except that there are a couple of dwarf clans that have allied with the orcs, and are trying to have the orc clans accepted as dwarf clans.
BTW, Eberron is designed not to have a lot of "sacrosanct linkages." Many aspects of the setting have no canonical explanation, often there are many suggestions about what might be true, there are lots of blank spaces to fill in, and the setting books always stress that you should feel free to change anything you feel like. And it's designed in a way that making changes to one aspect are unlikely to force a rewrite of other aspects of the setting. The setting has an organic feel, it's messy like real life, so there can also be exceptions to every rule.
For example, by canon King Kaius I of Karrnath was turned by the lich Erandis Vol into a vampire under her control. As a punishment she triggered his bloodlust resulting in him killing most of his family, which caused him to cease to be king. Probably. He was succeeded by his son Kaius II, who was later succeeded by
his son, Kiaus III.
Kaius III looks a
lot like his grandfather. And there is also a prisoner in an iron mask in the prison of Dreadhold, who is implied to be the real Kaius III, imprisoned by Kaius I so Kaius I could rule in his stead. Assuming that Kaius I has managed to find a way to prevent Vol from controlling him. Another possiblility is that the prisoner is Kaius I, imprisoned willingly or not by Kaius III, and the reason that Vol can't control "Kiaus III" is that he is actually Kiaus III, not Kaius I in disguise. The current king drops a lot of hints to those who think he might be a vampire to suggest he may, in fact, be a vampire, while also making various appearances that suggest he is
not a vampire. For eample, he has a habit of conducting business during the night, but occasinally does so in full daylight. He has a harem of fanatically loyal concubines either because he is really horney or because it lets him feed without killing people and leaving evidence (or both). He has sent Kaius III's brother and sister to the court of Breland either as a gesture of good faith and promise to keep the peace, or so they don't recognize him as an imposter.
So, the king may be Kaius I impersonating III, with III locked up in Dreadhold. Or the king might be Kiaus III pretending that he has been replaced by I. Or Kaius I and III may be working together, with III doing day shifts and I doing night shifts, and the person in Dreadhold is someone else entirely. If the king
is Kaius III, he may or may not be a vampire.
Also Kaius III (or I) has married an elf from Aerenal, a culture that is dead set against undead and has active kill squads doing their best to purge the world of them. Is she an agent of Aerenal ensuring that an imprisoned Kiaus I stays imprisoned? Is she there to ensure that the vampire king (I or III) has his bloodlust under control, it being too difficult/politically sensitive to assasinate a sitting king? Perhaps the king has an arrangement with the Aereni that they will let him live so long as he acts in their interests, and she is there as insurance (he is actively pursuing agents of Vol, for instance). Or is she trying to find out whether it is true that the king is a vampire? Or has she just fallen in love, and is supporting him despite her people's beliefs?
All of that may have relevance if you are running a campaign that involves name-level PCs getting caught up in affairs of state in Karrnath, but it won't change a thing regarding a campaign to try to stop the lizardfolk raids in Q'barra, or to fight criminal gangs in Sharn. Or if they are rivals of the Emerald Claw terrorist organization, which is a proxy of Vol's. Or even if Vol is directly an antagonist, but the campaign never goes near Karrnath. Until it becomes relevant, King Kaius the (?) is Schroedinger's Vampire King.