L77 self destruction
 

First post for me guys, as usual when it all turns to S...T reach out for help.
Background, I live in Western Austraila. Vehicle- Nissan Z32 (300ZX) with L77 engine and TR6060 box. This is my daily drive but I do the odd track day.
Dead stock engine tuned to 385hp on E85. Low mile engine 60,000ml.
So at the track last weekend the engine shit the bed. Unfortuately I just missed the pit exit when an engine noise started. Tried to gentle it round the lap but no she all let go and resulted in 2 broken rods, severly damaged crank and block.
Coolant temp was 210 at the time & oil 250 when the noise started. Dose not seem to be lack of oil pressure as all the other bearings look good.
First thing I found in the sump was a broken piece of conrod bolt, the other half is still in the piece of broken rod.
I just need some help trying to understand what caused this, from what everyone says these stock bottom end are good for 800hp+
Why would a rod bolt snap under relatively moderate load.