It's both. Viral replication gets the immune system into NK and T cell mediated killing mood, destroying even more of the remaining lungs and causing all result

It's both. Viral replication gets the immune system into NK and T cell mediated killing mood, destroying even more of the remaining lungs and causing all results of cytokine storm. Reducing viral replication would also stop the storm (with some delay). Apparently these drugs are not especially effective at it.