With dismay he understood why Kokoschka was not dead in Big Bear in 1988. Kokoschka had not made that trip yet. Kokoschka had only now learned of Stefan’s perfidy, when he had discovered the bodies of Januskaya and Volkaw. Before the public power supply was restored, Kokoschka would search Stefan’s office, find the detonator, and disarm the explosives. The institute would not be destroyed.
But how does that explain his presence in 1988 if you didn't kill those people yet to trigger him to go there? Ugh make it make sense! Did Stefan return too early?