Reading Fionn's posting reminds me of that wonderful advice I got once "Never assume malice, when stupidity is a sufficient explanation." No villains (except war itself) just stupidity, poor communications, and information overload.
There's a newspaper page I have seen reproduced in history books in which the ad by the German Embassy "Passengers are reminded that a state of war exists. . ." is next to the timetable of sailings for the Lusitania and the Mauritania, her sister ship(?)