Swadia and Khergits very often go bye bye without your help in warband.
Keep in mind the world being relatively static is based on the PC not getting involved. That's always been the point of M&B: Despite their constant warfare between themselves, factions rarely make any permanent gains of note.
From what I've seen of Warband, neither of these takes is totally correct.
I've done two saves of my own that corroborate this video.
Warband had flawed balance and appropriate
stability: Swadia and Vaegirs performed worse on the overworld map. Factions rarely died off without the player's intervention, but they could often make permanent gains and losses.
For comparison, the issues with Bannerlord:
1.3 Bannerlord's balance was awful and its
stability was way too low (Super Snowballing). Sturgia was total garbage, Khuzaits and Simps way too strong. Factions would either quickly die off before the player even had a chance to join them, or conquer the whole map within 5 years.
1.6 Bannerlord's balance was flawed and its
stability was good. Sturgia underperformed, Battania and Khuzaits overperformed. Factions would take a good amount of time to die off and territory would change hands fairly regularly.
1.7 Bannerlord's balance is still flawed but this is not noticeable because its
stability is way too high (Super Stagnation). Factions don't die off quickly which is good, but barely any territory changes hands, which makes the game boring and predictable and the vassal phase awful.
We are at the Super Stagnation end of the spectrum because:
* Bannerlord AI factions will quickly declare peace. Warband factions usually would not even consider making peace at the start of a war until a minimum period of time had passed. There should be hard-minimum and soft-maximum periods of war in Bannerlord.
* AI are too stupid to successfully complete a siege because A MAN HAS FALLEN INTO THE RIVER IN LEGO CITY across the map so they cancel their siege which is close to completion and leave and nothing ever gets captured.
* Garrisons never surrender to the AI (or player for that matter) even when totally outnumbered and their situation is hopeless, so every siege always takes a long time.
Ideally, I'd like the player to be the one to "swing the balance of power" as
@deuxhero said, so that barely any factions totally die off within 10 years without player intervention, but also I'd like to see factions make sizeable, permanent territory gains within the course of 20 years. All factions would be balanced except Battania (predisposed to usually lose rather than gain territory, to provide an "underdog" faction and match up with its lore) and the Empire subfactions (predisposed to usually fight to the death until at least one faction has been killed off within 20 years).
