The problem with that scenario is that there are eight other major power blocks.
Sure, some are cooperating. Others would indeed plan to take advantage. The bulk at least tacitly approved of, if not participated in the movement itself
Let me repeat that, with emphasis. Worlds close to a clan lord's heartland is much, MUCH more useful than worlds several sectors away, much less on the other side of the Great Rift.
The counter is that some Yerlyaruiwo propaganda would undoubtedly be effective in making the insult far more reaching as barbarian behavior. Others in the belligerent group would have their own agendas on various worlds in the Spinward Sectors of the Hierate. Others nursing grudges from the Border Wars. etc etc.
We have to agree that it can't just be single clan forces or even the single blocs, but at least a preponderance of the major blocs that agree together. IMTU, the main support from the Hierate was Yerlyaruiwo, Khaukherairl, Eakhtiyho, Aokhalte, Sahao, and Ouokhoi along with the megacorps Tlasayerlahel and Wyaroaer to support it, as well. Ostensibly Yerlyaruiwo was avenging the death of their ambassador and punishing the barbarians and others answered their call. They got a majority of the Tlaukhu to endorse a limited response to the barbarian atrocity specifically while retaining the general Peace of Ftahalr. But there was a building resentment over the "Minor Race" propaganda from the Barbarians that was being exploited, as well, but also a call to duty and the betterment of the species.
Certain factions would have preferred to to move against the Solomani and many clamored for the most obvious strike against Ilelish, but similar to the US and Iraq vs Afghanistan, other voices convinced them that the Spinward Sectors were more important for various reasons. That placated some of the criticism. In the Tlaukhu, they were able to get the endorsement by also issue a proclamation on their honor that they weren't going to attack other Fteirle during this movement, as they declared they were acting for the Fteirle everywhere. Some of their more idealistic, if not gullible rivals bought it wholeheartedly while cynics decided they could also take advantage. Others no doubt laid plans to try to capitalize on their local enemies... but the analogy IMTU was almost like Europe in the Crusades. Many of the most prominent players are participating, even normally hated rivals (Platanaget, Capetian, Angevin, etc) and those of the rest are under implicit agreement to not take overt advantage. Some will anyway (infamous stories of John while Richard is away, Philip the Fair when he gets home, etc while others have their own problems anyway. The point is that it's easily possible for the movement to take on a life of it's own and grows bigger than the Yerlyaruiwo intended, including amongst their own vassals so much that they were exposed as vulnerable to the Tralyeaeawi. Indeed in one of my brief overviews of Aslan Space in the New Era, the greater Hierate did Collapse after a slower penetration by Virus but there was a particular strain that was from Yerlyaruiwo areas that was focused on vengeance against anything related to the Tralyeaeawi...
So what happens when a clan suddenly sends off a significant fraction of its forces on a mission that will keep them busy for years? That's right, its neighbors suddenly remember an intolerable several century old insult that just HAS to be avenged. Honor demands it!
The participating clans didn't just leave themselves defenseless, though. The alliances sort of covered each other, but otherwise also raised themselves to wartime production to support their endeavors. Their rivals were dissuaded from full-scale war by both the tacit agreement of the Tlaukhu and the simple fact that with their rivals were on war footing it could easily turn into a legitimate full scale semi-civil war. When their rivals remained more focus on new territory
He's certainly much more concerned about an expected Zhodani attack. At first. But as the months pass and the Domain really gets on a war footing, increasing military spending by 500%, reactivating mothballed ships by the score and hundreds, and new construction getting on line, and the Zhodani never showing up... eventually he'll beging to feel that he can afford to divert a few squadrons to the rimward border. And the more of a threat the Aslans are, the more incentive he has to send ships off to beat the pesky Aslans back and teaching them a lesson before the Zhodani show up.
Well ultimately, it's about whether you want the OTU events to proceed or not. You have enough imagination to enhance the stuff behind the scenes, but if you seem want to butterfly it away, that's easily available, too. I think some always overestimated the actual scale of the Imperium but that's where TU differ from each other.
IMTU, the Zhodani not being interested in conquest (since they have their own problems) is barely a relief to Norris because he's cut off from the greater Imperium (and the Domain of Deneb never been entirely self-sufficient anyway) and up to his neck in Cats and Dogs.
