First of all, since this was the Navy, it very well could be that the "passenger 737" was actually a Navy P-8 Poseidon reconnaissance aircraft, and this was part of an exercise for the ship's CIC.
Second of all, if the CWIS was armed, sailors would not be allowed on deck at all. So the fact that the sailors were filming and joking indicates the weapon was not armed, and if that was a civilian 737 it was in no danger.
What’s the effective range of Phalanx? A commercial jet at cruising altitude is not “Close In”