Small precision: the 5th fleet headquarters were hit (in Bahrain), not the fleet itself.

Without the headquarter however their capabilities to deploy could be severely reduced, depending on how big the damage is and if the US has contingency in place for someone else to take over fleet command in the meantime. The fleet can operate independently to an extent but it's not just this one base of course, Iran struck reportedly 14 bases in the region. This could (or at least was probably the goal) force US ships to leave the strait entirely. A ship can't stay forever at sea, it needs maintenance, personnel rotation, and supplies.