One interpretation is that the Union needed a visible defeat of Mobile's defenders. Destroying ships and taking forts would make it harder to claim that the Confederate military remained undefeated in the field. An analogy with later narratives about Germany after the First World War illustrates that psychological problem, without treating the cases as identical. An operation's political effect can depend on the perceived decisiveness of the result as well as its material gains.
Notable Point · 3:16:45-3:18:06
Why Mobile Bay needed a visible defeat
Closing the port mattered, but destroying its naval defense also denied the Confederacy a story of continued military resistance.