I've started a couple of messages on this - and then demurred because the only way to put the logic together is to wander into hypotheticals that muddy public discussion.
So, leaving out the analysis and stating only my long pondered conclusion (aka 'guess') about how this could have happened, I agree with Plastic Bug that bad luck was likely a big factor, and with Volume that progressive mechanical deterioration after a brief violation of the envelope probably was the mechanism.
I think it plausible that the entire failure process may have derived from the second wake encounter alone, and that the basic failure could have happened within a second or two after the wake hit. The combination of a very strong initial sideways push on the tail, plus some resonances in the airframe, plus some out-of sync responses from the yaw-damper and other controls collectively may have caused the tail to rebound through centerline so fast as to cause vtail stall eddies that fluttered the rudder, promoting a prolonged oscillation of the physical and electronic controls that fairly quickly tore up the rudder and in so doing horsed the tail around so much that it succumbed shortly thereafter. Any significant control input from the crew would likely have sought to damp uncommanded rudder excursions, but the rudder might well have been chaotically unstable in the flutter mode and thus inclined to change dramatically in pitch with only minor control stimulus.
If this is what happened, a bit more delay in the control responses to very sudden displacements would be a plausible fix to avoid recurrence. And a bigger / better flutter recovery algorithm.
Whatever the nuts and bolts, it's all terribly sad. May they rest in peace.