Complex sentence: Emil Burbank was recruited to the Squadron because he was tested by the military and found to have been exposed to the retrovirus that had been released from Hyperion's spacecraft and bestowed superhuman abilities on numerous people around the world.
Split into simpler sentences: Emil Burbank was recruited to the Squadron because he was tested by the military and found to have a retrovirus that had been released from Hyperion's spacecraft. This virus bestowed superhuman abilities on numerous people around the world.