car bump confused???

Hi... last week I was travelling approx 10mph (just pulled off from trafic lights) when I took my eye off the road as my kids were fighting in back. The car in front had braked suddenly which I didn't see until I hit it. Then this caused the car behind me to go into the back of me shunting me forward back 2 the car in front. The car in front had a tow bar on which has damaged the front of my car. I had 2 get the car towed as it wouldn't start. Now the insurance are saying the car is a write off. I'm confused as I didn't think much damage had been caused as the air bag didn't deploy.
My car is a 57 astra 1.6 sxi. Can any1 she'd some light into what the actually damage could be as I really don't understand it all.
Tia