FWIW it was an Avidyne display.
There are a host of reasons why it could have been CFIT - NOT suggesting it was.
There have been cases of Avidyne's failing and with this system the PFD couldn't be switched to the other screen, the autopilot might have failed or tripped, or the pilot may have chosen to hand fly, to suggest a few.
Without the PFD flying on the standby instruments will always be more challenging, and while the autopilot can be driven form the Garmin's you need to know how to do this.