I wonder if what is blindsiding all of these companies and people is routing.

That if you have a box that can talk to network A and B, suddenly anything on A can talk to anything on B.

A CAN bus, or older modbus installs, would be airgapped by its very nature.

Just because its CAN doesn't mean its actually air gapped. If there is a Linux box on one end for SCADA use or similar, then the path is IP -> Linux spl01t -> SocketCAN