Perhaps, if we're willing to put K8P first for a moment, we can think of this as an opportunity.
Currently, K8P has a lot of money from reclaimed loot. Once the Okral leaves, it will have infinity money from the vaults. Once the We's silk is online, we'll have double infinity money, part of which is coming from a valuable trade good.
Now, over the course of the reclamation and aftermath, Belegar's been racking up IOU's all over the place on the premise that the king of a resurgent Dwarf Hold can certainly make it worth their while, and what better opportunity than a trade crisis - an issue which can be at least partially resolved by the application of money and trade goods - to pay those back and then some?
If Belegar played his cards right, he could use Marienberg's embargo to significantly increase his own soft power and probably even get the We silk through the doors of the more conservative prospective buyers, which could pay back his monetary investment in the long run and further increase reformist pressure and Belegar's personal support in the Karaz Ankor.
As for why we'd want to increase Belegar's soft power? If he does rack up enough influence in the Karaz Ankor, and it becomes clear enough to Thorgrim that he needs to do something about the tension between the holds, that could, maybe, lead to Thorgrim labeling Belegar as his heir at some point. Which would allow the truth about Waystones to come out, hopefully easing the tension, and set up the Karaz Ankor with a future High King who was a little more open-minded.
Buuut that's far out and highly speculative. The potential for repayments of debts, increased trade contracts, and increased soft power for K8P? That's downright likely.
It just comes at the expense of, you know, everyone else. Some provinces will be feeling the pinch in the old military from this, and lord knows Talabecland won't be happy, the peat-smuggling fuckers.