Ain't it because that delivery project became successful? After that they began to extend their business to the East territory. They exported goods from the east which became popular. Since it is hard to go the East region due to its distance, only few merchants can get their products but because Tia came up with idea to use the river on his father's territory, they were able to go their easily. And they made a "cruise" business out of it too.
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The empress asked the emperor to give permission to investigate Pellet corporation and arrest Clerivan. She accused Pellet corporation tobbe the mastermind of giving Astana the drug which made him hallucinate and attack the emperor. Obviously Astana got arrested because of that and even lost his hand if I remember it correctly.
But the real reason of the Empress is to get the contract from Pellet Corporation. Empress Lavini borrowed money from them and agreed to make some of their territory as collateral. Obviously after they failed the Western project (where they need the triva trees) and were unable to paid their debt and eventually lose their rights to govern some of the cities in the West. (Note: Angenas is the representative of the West)
Iirc she only revealed to the vassals and other families that she's the true owner of pellet union at the end (when clerivan was arrested for something?) I can't remember much anymore.
What did she do again to make the heads trust her during her "start up" business again?