Detailed Explanation
George's death is what sets everything in motion. He found a hard drive with information about the outside world—proof that the silo's rulers have been lying to everyone. He was killed to silence him, but not before passing the drive to Juliette. What I found chilling is how the murder was covered up as a suicide. In the silo, anyone who questions the system tends to "choose" to go outside—dying from toxic exposure. It's the perfect system of control: make dissidents seem crazy, then eliminate them publicly.