Not all tragedy is the result of guilt, but guilt can lead to tragedy. This is the same answer that Jesus gave in the first example. Jesus denies that the eighteen were worse offenders than other Jerusalemites, but uses the opportunity to call his listeners to repentance. Again, his purpose is not condemnation but redemption. The call to repentance shows that it is not too late.
Salvation is still possible.
By the time that Luke wrote this Gospel, the Romans had destroyed Jerusalem and had killed most of its inhabitants. We need always to be repentant, because we never know when a tyrant will rise up against us or a wall will fall on us. Neither the Galileans who were killed by Pilate nor the eighteen who were crushed by the wall had opportunity to repent. The end came swiftly-without warning. So it may be with us.