Why was Frederick William disappointed by the Peace of Westphalia settlement in Pomerania?

Frederick William, the Elector of Brandenburg, was disappointed by the Peace of Westphalia settlement regarding Pomerania because he failed to achieve his primary goal of acquiring the entire region.1

Specifically, he sought control over the Oder estuary and the strategically vital harbour of Stettin (now Szczecin), but these territories were awarded to Sweden under the terms of the peace. Lacking the support of powerful allies at the peace congress, Frederick William was forced to settle for eastern Pomerania, along with the secularized dioceses of Minden and Halberstadt and the promise of the archbishopric of Magdeburg. While these acquisitions were important for connecting his western German possessions, they fell short of his broader territorial ambitions for the region.12