In this particular case, it's because the CAN bus shares two wires across all devices, with everything connected in parallel. Water ingress or catastrophic fail

In this particular case, it's because the CAN bus shares two wires across all devices, with everything connected in parallel. Water ingress or catastrophic failure to any of the wires, connectors, or terminations/devices can result in an open or short circuit, or at least enough load to cause the signal drivers to be incapable of driving the right levels. Although this particular example is from what some would consider a controversial video, this is an example of how water ingress can result in the disablement of vehicle electronics: https://youtu.be/Gio3DSTkQH4?feature=shared&t=181 https://youtu.be/Gio3DSTkQH4?feature=shared&t=181