From a quick first pass of the report main issues IMO:
PIC did not believe that MRGB lube oil was gone due to false "normal" temperature indication. Pump failure was suspect as cause of no lube oil pressure. But temperature should have increased with activation of bypass switch which was done very late. This was a key miss by the PIC IMO.
Only when T/R drive failed did they know for sure.
Sad, very very sad...here's hoping the TSB recommended changes make this scenario a thing of the past.
Safe flying
Max