I wouldn't label it as "win the war", if you were on that campaign you would likely utilise most assets to bring about a quick victory.
It is utilised as a strategic deprivation, CVs are powerful assets, and they stay in ownership of the country that controls the port at the time they respawn. If a country captures a port and the CV in enemy hands is not sunk, the country in control of the port is deprived of its CV.