bearfoil - Ah, I see, I think. Your interpretation of events may not coincide with mine. In particular the term 'explosion' is a bit loose.
This is the general progression of the failure as I understand it.
1. The oil pipe failed and oil found itself where it shouldn't be, in an environment condusive to combustion.
2. Oil caught fire and burned with sufficient ferocity as to degrade the material of the IP shaft or coupling. Although fairly exciting, there was no explosion.
3. Shaft or coupling failed, disconnecting turbine disc from its compressor.
4. IP turbine disc oversped to burst in classic tri hub fashion. It did not explode, it burst. The effects were similar to those of an explosion. But the professionals use the expression 'burst'.
Is it your belief that there was some kind of explosive phenomenon taking place in the bearing chamber which in some way 'exploded' the disc?