Was it? I’m looking at all the sources that claim it did, and they seem to all be on the left. Torpedo impacts would have set off such munitions, besides, but it was only the torpedo damage that sank the ship.
Lusitania divers warned of danger from war munitions in 1982, papers reveal
https://www.theguardian.com/world/2014/may/01/lusitania-salvage-warning-munitions-1982
Now who was leading Britain in 1982?