Given that the Lucitania was about the fastest ship on the run would the Germans have any way of knowing what was on board at the time of the sinking?
Surely all the post event discussion is just an attempt at justification. These ships didn’t waste time in port they would turn around as quickly as they could. Finding what had been loaded wouldn’t have been hard, the docks would have been full of spys, but how could the information have been conveyed back to Germany, processed, a decision taken and the instruction sent out to a U boat captain at sea? I don’t think it could. There was a transatlantic telegraph cable but it came to UK and we wouldn’t have been passing on messages. Would a U boat that far out have been in radio contact in 1915?
My take is that the ship was sunk where it was because the U Boat was either waiting for it knowing it would have to round the southern tip of Ireland and it was all planned way in advance. Or that the sub was waiting there for a cargo ship and it was a spur of the moment thing.
I don’t think though the sinking can be justified retrospectively by saying it was carrying ammo, even though it was.