The Spike Protein of the SARS-CoV-2 virus has been shown to cause damage to mitochondria via its interaction with ACE2. As mitochondrial components enter the extracellular space, the immune system misreads these components as an infectious agent. 

In addition to this, the Spike Protein's antagonistic binding to a7nAChR receptors activates Mast Cells and contributes to their degranulation.

This explains why a Coronavirus (which before any of the SARS viruses appeared was, overall, quite harmless) has become the instigator of catastrphic immune events. It is because of the Spike Protein. I believe the Spike Protein has been engineered to 1) initiate an extreme inflammatory response on its own and then (in susceptible individuals, perhaps all if the Spike had been further refined) 2) TRANSITION that extreme EXOGENOUS inflammatory response to an extreme ENDOGENOUS inflammatory response, causing the body to destroy itself in devastating storm of cytokines.