The nasty part about an attitude system failure is the crew can follow erroneous indications until it becomes apparent that the aircraft is in a very bad place.
By this point the other attitude sources will also be showing unusual attitudes and the crew will likely be in a situation they have never seen or trained before.
Lack of air data makes it difficult to demonstrate such a failure in a sim with good fidelity. Should we do certain upset training in military trainers?
Were there alerts for attitude systems disagree? If so, they seem not to have gotten the crew's attention in time
