Actually, there is more to this than meets the eye. With the Nimitz in the Persian Gulf, the ship is essentially bottled up - contained in terms of limitations of maneuvering (one way in and one way out - through the straits of hormuz which is incredibly narrow). Having the Nimitz positioned out in the Gulf of Oman, maneuvering is not longer a problem - it actually becomes a tactical advantage. Iran is still within striking range (yes a bit farther in distance), but there are also a wide range of secondary airfields available. There is also lots of tanker availability with air cover for the egress of the sorties. Repositioning the Nimitz provides it with a greater tactical advantage and greater freedom to maneuver.