When I saw the AF447 rudder I noticed one thing. The Forward Attach Point (nut) was still on the rudder and the aft one was missing.
I am not a accident investigator but studied it extensively in college, and what I deduce is this:
The forward attach point would have sheared on impact with the water if if was attached to the fuselage. Because the back one was missing I think it is reasonable to suspect large rudder or vertical stabilizer oscillations that caused the Afterword Attach Point to shear.
Now granted this is just off the new photos, but it was in very good shape.