AFAIK all modern passenger a/c are designed (possibly even required) to operate with reversers deployed in-flight. It's not even entirely unusual for it to happen - the media made it out to be after the Lauda Air crash, but I mean, they use reversers occasionally as air brakes in some aircraft. I suppose in a twin-engine plane a surprise deployment would be a bit more troublesome than on a four-engine aircraft, but investigators determined that even the Lauda Air crash was avoidable if the pilot had taken immediate corrective action. They did not blame the crash on pilot error, however, because there was no training program in place for this kind of failure at the time. Nowadays, pilots are trained for an in-flight failure of the reverser locking mechanism. It is not, by definition, a catastrophic failure, especially not at 270 knots. It would not cause an engine to separate from a wing, much less two of them (both engines were found in separate areas away from the main wreckage).
I dunno what caused this crash, but a reverser problem seems unlikely to me.
I'm tired of being a wanna-be league bowler. I wanna be a league bowler!