Complex sentence: He discovers the "bombings" were triggered by soldiers subjected to Hansen's Extremis, which at this stage of development caused certain subjects to explosively reject the treatment, with the explosions being falsely attributed to a terrorist plot in order to cover up Extremis's flaws.
Split into simpler sentences: He discovers the "bombings" were triggered by soldiers subjected to Extremis, which at this stage of development caused certain subjects to explosively reject the treatment. After veterans started exploding, these explosions were falsely attributed to a terrorist plot in order to cover up Extremis's flaws.