A coworker for a nearby team died of natural causes in his home this past weekend. He would have been around 30 years old, so his death came as very sudden and unexpected. We tend to ask "why" a lot more when a younger person dies, than one who is 80+.
Jesus was asked about some tragic deaths in his day (Luke 13:1-5). Apparently the same Roman governor, Pilate, who would enable Christ to be crucified, also sacrificed some local Israelites. People began to wonder, "why were these people killed? What sins did they commit to deserve this?" Jesus breaks up this cause and effect thinking by stating that these Galileans were no worse sinners than any others. He also brings up the structural engineering failure of a local tower that collapsed and fell on 18 nearby folks, killing them. They too were no worse.
Death becomes incredibly frustrating when only looked at through the lens of this life. It's impossible to say God is fair when looking at how things are dished out here. Karma's cause-and-effect mentaility convuludes death, and Jesus rebukes the notion. Possibly Jesus knew those Gallileans that Pilate sacrificed. There's no question that there death was tradgic and incredibly sad. But Christ is able to watch this world spin its course (even when bad things happen), because he knows that's not the end of the story. There is more to come, where rewards can be given, debts can be relieved, and punishment can be handed out.
As a result, Jesus' application for those shaken by the death of the Gallileans was about controlling what they can. The examples in the passage or the case of my coworker show that death is largely out of our control. What is within our control is to repent and work on bearing fruit. This is the direction Jesus pushes his audience.