Fuel contamination can be a very critical factor in the everyday operation.
I've got to admit that it sure does cross one's mind in many incidents with misbehaving engines, although I can't think of any confirmations in a couple of decades
Multiple engine events are almost always common-cause inspite of what most imagine flying ETOPs routes with only two engines. And indeed wear out modes or computer cock ups would be extremely rare in a single flight without having been exposed by numerous write ups in a fleets history.
Most everything now-a-days having to do with complex aircraft system interactions has been considered and "fail safed" to the point where the aircraft just won't fall out of the sky albeit the pilot workload may be increased. This seems to be the case here so I'm still open to some of the responses being secondary to a fail-safe design response kicking in from whatever was the common cause that started it.
I'm sure that they are going to look at the aircraft system interaction with the engines very closely seeing as how the engines didn't seem to pack it up with parts out the tailpipe.
I sure hope some more clues come into this thread eventually