@MadMike What do you make of all this?
Nothing too meaningful I can add to be honest.
An "arrested" ship isn't an uncommon thing. It usually means bills or fines were not paid (finance, bunkers etc.), the people owed money went to court and got an arrest warrant for the ship, which was then forbidden from sailing unless debts were paid. The ship's 34-35 years old according to my db, so it's past the end of its life. Usually those get sold for scrap, but often a shady owner might take it on and operate it (usually in nefarious practices) till an event like an arrest. Then the owning company either quickly dissolves in a bankruptcy file or fully disappears into the shadows, leaving the port operators with a ghost ship on their hands.
This kind of stuff is quite common for ships operating illegal routes or moving contraband material. Not everyone can afford the risk of having a spanking new £100m ship getting arrested for trafficking drugs/weapons/humans and having to come forward to claim it. So usually it's done through these old beat-up vessels who's ownership lies in layers of obscure companies so when you try to untangle the yarn you get nowhere.
The ship was operated by a tiny company out of Burgas, Bulgaria who obviously couldn't be contacted the second the ship got arrested. If that gives you any clue. Could be the fertiliser was contraband or was intended for hezbollah bomb-making? Your guess is as good as mine.