Many of these systems have a management UI available through mobile devices because of the need for staff to manage them while in the field or out of the office

Many of these systems have a management UI available through mobile devices because of the need for staff to manage them while in the field or out of the office. As I said, some of the most critical systems are air gapped but there are critical systems that require an internet connection for practical use. Emergency dispatch for example - the airport acts as a PSAP (https://en.wikipedia.org/wiki/Public-safety_answering_point https://en.wikipedia.org/wiki/Public-safety_answering_point) and requires integration into regional systems. They have radio backups but my understanding is that they pull a lot of data via the internet. The first responders also have cloud apps that help them route to a location or see the position of other nearby resources. There is also considerable coordination with regional/national infrastructure owned by the airlines for managing when aircraft will depart/arrive. That would be much harder without an internet connection. The airport will continue to operate safely if they lose internet connected infrastructure but the efficiency will drop quickly and the national airspace is like a busy road network - congestion in one area can rapidly cascade and cause chaos.