After a couple days in the back of a truck, I can understand why it was difficult to determine the cause.
It would take a couple days to cool off the bodies and clean out the larva.
Your point is taken, but probably not that. There in the mountains behind Santa Cruz on the coast, temperatures are mild year round and the forecast high for tomorrow is 73 with lows in the 40s. More likely, bear in mind that is hard core real heavy redwood forest with all of our little woodland friends present. More likely the fauna snacked on them, than decomposition