old engineer
I agree with barit1 that it is unlikely that a compressor stall was the start of this.
I don't think anyone suggested the compressor stall started the chain of events leading to the engine failure. It was primarily a discussion of the two "bangs" heard and reported by the flight deck crew. The reality of it is though, when the compressed airflow of the IP compressor (N2) significantly dropped (no IPT drive), the HP (N3) compressor eventually choked and stalled, especially if it was in a increasing rpm mode to create thrust as demanded by fuel flow to the combustor. This was the situation as I see it. A HP compressor stall was inevitable.
I also see a large, clean ball thrust bearing, with a buckled outer race.
When you look at the views of the engine presented in the ASTB report, I think everything you see is from areas to the rear of the combustor casing. You can still clearly see the complete combustor case with the fuel inputs and electrical igniters, the wires shielded with a reddish insulation, as the engine is being removed from the pylon. I don't believe there was any destruction of the compressors or rupture of the compressor casings (IP or HP), that would release thrust ball bearings. I have seen compressor failures on engines, and the results are really not pretty, even more catastrophic in appearance than on this engine.