I am sorry to hear about the accident, and glad you are ok.
From my 97 540 owner's manual: "Deceleration sensors continuously
monitor the physical forces acting upon the vehicle. The system responds to the extreme deceleration rates associated with high-intensity impacts - of the kind in which the safety belts alone might not be able to provide adequate protection."
So the computer probably determined that the accident did not require anything more than seat belts to keep you safe... It was obviously right, as you said you came out without injury.
As far as the doors not unlocking, they will only unlock if you used the central locking button to lock the doors. Perhaps you locked the door manually, or didn't lock the doors at all?
I don't know why the hazard lights did not come on... perhaps they are linked somehow to the airbags, and only come on if the airbag deploys?
And the interior lights are supposed to come on as well. Perhaps also linked to the airbags, or maybe they did come on and it was still light enough outside that you didn't notice?
Anyway, I would be grateful that the car protected me. You said yourself that "I am physically untouched--BMW's really are built very strongly." I would agree with you. Your car did it's job to protect you. Perhaps if you had been injured, you would have a case against BMW for not deploying the airbags properly. But, you seem to be ok, and now it is up to the insurance companies to work out getting your car replaced.