Sounds like a pretty big accident if multiple airbags and etc.
Did the title get changed?
I'd take it up with CarFax under some circumstances they'd be responsible for buying the car back, but I'm sure the limits on that are pretty well leaned in their favor.
https://www.carfax.com/manifest/bbg/termsConditions.cfx
BMW may or may not allow CPO on a car with damage, but if the damage was repaired to BMW specs and it wasn't on the CarFax it could be hard for anyone, including a dealer, to pick up how extensive the damage was.