this happens quite frequently, but it also hints you on how to cheese the game. Basically recruit any clan you can no matter what that has 3 parties. (main guy + 2 vassals in their list), once you've recruited enough of these bad-boys they'll run around wreaking havoc every war you get into. Then there's the geo-location issue, you won't do much if you start either by Sturgia or any of the Empire lands (although the main quest kinda allows you to gain something from the bleeding you'll take by using their central lands, once you've completed stage 2 after reforming the empire you'll absorb all remaining imperial clans, meaning that at minimum you'll get 3 strong former ruler clans into your wing). If you go the Empire route and absorb them successfully the game becomes pointless.
Now, to a more grounded cheese strategy: Recruit at least 5 big clans, and start your kingom on one of the map corners (Khuzait lands / Vlandian Lands / Aserai Lands) as long as it isn't Sturgia. After that you can eat your way up because your "starting corner" will be mostly safe. You have, though, to grant lands to all recently recruited lords ASAP, if you don't you may lose them, and if that happens you must track down those same blokes during peace time because you can instantly re-recruit them skipping that ridiculous RNG persuasion.
Now, this latter path is more interesting, but cheesy none-the-less, because of how the game works. So, having a corner kingdom with enough big clan vassals translates into a practical steam-rolling, you'll have no issues what so ever and the difficult part will only really be the first 10 fiefs, after that you'll have enough muscle from your vassals to actually just relax in your town, RP, do crafting. You can, however, continue expanding. One way or another the game gets cheesed and the same result issues: Boredom.Unbearable boredom.
Until TW applies proper diplomatic solutions, more options for play-style and late-game content, you'll always get bored if you reach late-game, and the path to reaching late-game is quite annoying for it's extremely narrow, it's not open nor can it happen without doing things on a very specific pattern and sequence. Also, if you delay somewhat before you set out to do it, the same thing that has happened to you "endless stream of 1500 armies" will certainly happen again, because you've allowed the AI to snowball before joining in the fun.
Particularly, and quite frankly, I don't like BL, but I keep in mind that the game is unfinished and it's somewhat bound to improve, but (_|_) looking at the RIGHT NOW, at the present, and being realist about it, to me the game simply sucks. (if you look at it under a practical point of view). I hope it improves, I know ways of it improving, but I doubt it'll happen anytime soon. Currently there are issues basically on every single aspect of the game, from Character Progression, to off-shoot narratives, quests, lack of input by the player, lack of interaction, lack of content, and ultimately excess of grind. The fixes for these issues were stated over a million times in the forums, and I can safely say that most of us know them to hell and back, what changes are the tones and the relative views people take and talk about. Yes, the game might improve (some believe it will with all of their strength), yes it's an EA, and yes it's a "testing phase". Though none of that changes how we feel about it. Some clueless people are asking for this, others for that, others for that-that, and in reality, we shouldn't be asking for any ****ing thing, we will only really be able to understand what we want once the game has reached a certain stage where all of it's content can be at least felt (not necessarily finished), and this day is far, far away. Requesting or preoccupying with balance is just a waste of time because any balance done now cannot be kept for the "final product". Hence why I don't think the best course of action is to request changes, I've come to the conclusion (in the past week) that the real best course of action is to simply put the game aside and wait for significant updates, so far nothing really significant was added, so it's more of the same with "some caveat".
So far they are balancing and aligning a three wheeled car, which no one could possibly take on a long trip, so the journey is still bound to be short and weird, so the feedback we give on said car is moot, because everybody knows that the car must have 4 wheels before it can be properly used. That's basically Bannerlord's EA. Problem is that not everybody can make that co-relation, many do not understand that there's a wheel missing :/ and so they rage, they flip, they ****post, they make absurd requests, and more importantly: They keep asking for balance adjustments.