Engine Shut Off Without Warning problems of the 2013 Audi S8

While driving on the main highway, my car engine shut off. I had dysfunctional brake and steering failure. Brake was hardly working and I had to use all my strength to control steering. Basically, while driving at 50mph, car engine shut off without warning and I lost steering and braking. I was able to pull off the road into a vacant parking lot and car came to a stop. Fortunately, no cars were around at the time. Otherwise, I along with my family would have been involved in a potentially fatal accident. My car had been serviced by Audi since purchase. It was just serviced within the past month. Car was towed to an Audi dealer--the turbo charger had failed. Based on the dealer description, failer of turbo caused the catastrophic failure of both the steering and the brakes. There should be a backup safety mechanism in case of turbo failure with Audi 4l engine--apparently, this does not seem to exist. I contacted Audi and they had no explanation. It was just by god's grace that horrible accident did not occur. I hope you can provide some insight into this. Based on some blogs, this is apparently common with 4l turbo engines with Audi.