Adaptive cruise control will detect a stopped car and come to a complete stop - but only sometimes. Might depend on speed difference or even the color or shape of the car or object. So it's very possible that the car stopped in previous situations, and the driver completely expected it would do the same, especially with such a large emergency vehicle with flashing lights. By the time the driver realized the car did not detect the emergency vehicle, it may have been too late.

These systems are unable to detect when intervention is required.