Originally Posted by
Concours77
... If the failure originated in the rear of the joint, the blade would immediately try to unpeel forward causing the tip to migrate well ahead of the fan’s plane, perhaps explaining the lack of evidence of major contact damage to the blades bracketing it?
...
I believe in one of the NTSB briefings it was said that the crack was at the rear and would not have been possible to see on a visual inspection from the front (I think it was in Q&A and that was the question). At some point after separation we know the blade itself fractured into at least two pieces - because the NTSB have the root half but not the rest - but what caused that we can only guess. I doubt it was impact with the rest of the fan because (as you say) what we've seen shows surprisingly little damage there.