Alternatively… Why do people think nuclear weapons are something that can't be 'wasted?'
I think the answer to a lot of this is more mundane than nuclear weapons - yet also more damning in the long run, but more difficult to explain. It's not the "aha!" Moment of coming across a grand conspiracy to blow up a warehouse.
We know hezbollah and related terrorist groups manufacture weapons. Ammonium nitrate is a key compound used in rockets and explosives. A Russian/Ukranian guy could send a ship down to one of these ports (or a captain could just defect with the cargo), the local authorities could seize it (and who knows what the paperwork says they found) - it goes into storage and can then be pilfered from as a strategic supply for manufacturing to produce less-crude IEDs or even some proper munitions grade explosives.
What we are seeing unfold throughout the middle east with sabotage incidents is likely two prong. First - the media is suddenly reporting on industrial accidents and/or they have entered the public sphere of discussion so as to cloud which events are acts of sabotage and which ones are just run of the mill accidents.
The second part of it is that there are likely a number of shadow ops being carried out to shut down supply and manufacture for various terrorist groups and it is likely multinational with black ops doing their thing (and it doesn't really matter who your sponsoring nation is in black ops - you run across people who do things and their sponsoring nations give them slack in their leashes).
It could also be that the whole plot to import fertilizer and store it in such a way was the attack, itself - and all that needed to be done was assign some hapless welders to go do a job and set things in motion.
I lean more heavily toward the first idea - but the second is also plausible.