Declaring a fuel emergency doesn’t mean that they have run out of fuel, or that they will run out of fuel soon. It means that if even they diverted to their alt

Declaring a fuel emergency doesn’t mean that they have run out of fuel, or that they will run out of fuel soon. It means that if even they diverted to their alternate right now, they would expect to go below their reserve fuel level before they could land. The reserve fuel level is there to give them an extra half hour or more of flight time. Absent some mechanical problem with the engines, or a fuel leak, declaring a fuel emergency would mean that the pilots waited too long at their destination airport before thinking about diverting. You’re supposed to simply divert _before_ you would need to declare an emergency, rather than declare an emergency simply in order to skip ahead in line. There was no risk of a crash in this circumstance, because the plane still had plenty of fuel to divert to their alternate and land before going into their final reserve.