The passengers of the Lusitania believed because they were on a luxury passenger boat rather than a military boat that opposing forces i.e. the Germans would not sink or attack a boat that was merely carrying people. They simply figured since they weren't fighting or in the war that their travels should not be affected. During this time it was common from Allies to send supplies including weapons via passenger boat when the Lusitania sank it was noted that there was supplies on it to help the Allies.
