A 45-year-old man with severe P. falciparum malaria (parasitaemia 20%) develops acute respiratory distress syndrome (ARDS) on day 2 of IV artesunate treatment, despite falling parasitaemia. His oxygen saturation is 82% on 15 L/min oxygen via non-rebreather mask. Chest X-ray shows bilateral diffuse alveolar infiltrates. What is the most likely mechanism of ARDS in severe malaria?