Maybe. Just maybe someone broke into the car when you had it and stole the airbag (easy to steal and expensive to buy). Hence the vehicle worked when you drove it and then suddenly had issues.

Or one of the employees smashed the bumper moving it and ripped the deployed airbag out to cover it up.

Yah, rental companies amazingly blame good paying customers for whatever.

Please do not pay. The reason rental companies continue with these criminal practices is that some people just pay.

They have no proof. They received the car and checked it over and signed off on it.