What I see is that their population possibly weren't as invested in the outcome as that of the Imperium. Imperial citizens/subjects couldn't avoid the war, whereas the Solomani were seeing their children being fed into a 13 year long meatgrinder with little obvious benefit. That's plenty of time for war-weariness to take hold.
Furthermore, a lot of the fighting they were doing took place on and around lots of high population worlds. That's a rather different thing from the giant space battles that were the main event elsewhere.
To make it worse, right at the beginning they swallowed the poison pill of Old Expanses, where they took in an entire sector's worth of an essentially unreconstructed part of the Imperium. That was a major shift in the balance of power in the Confederation, which, after all, was previously only about four sectors in size.
And, of course, the Confederation was, despite SolSec's efforts, a confederation of what were in many ways rather loosely associated regions.
Essentially, they bit off more than they could chew.
At least that's my take on it. No, it doesn't really make sense.
Furthermore, a lot of the fighting they were doing took place on and around lots of high population worlds. That's a rather different thing from the giant space battles that were the main event elsewhere.
To make it worse, right at the beginning they swallowed the poison pill of Old Expanses, where they took in an entire sector's worth of an essentially unreconstructed part of the Imperium. That was a major shift in the balance of power in the Confederation, which, after all, was previously only about four sectors in size.
And, of course, the Confederation was, despite SolSec's efforts, a confederation of what were in many ways rather loosely associated regions.
Essentially, they bit off more than they could chew.
At least that's my take on it. No, it doesn't really make sense.