Air bags fire when the accident is server enough to warranty them. A sore neck, and the “radiator smashed” are NOT severe enough. If the airbags in a modern car fire, even if it’s just the drivers and passenger side font bags, they require replacement (and usually parts of the dash too) that would add around £1200 to the repair cost.
I bet you were twisted in your seat when you hit the car in front, so you slipped out sideays from the seat belt, hence your torso pivoted forwards and you face butted the handwheel!
These “i though he was going, then he stopped” kind of accidents are common, easily done, and one of the few areas (IMO) where the latest collision mitigation radar systems fitted to modern cars actually work pretty well!