If an inconvenient party is responsible--like Hezbollah or Iran directly--fingering them is going to be very dangerous for the accuser. So how do you pretend you have no idea who did it?
Honestly, the investigation seems designed to avoid determining who caused the detonation:
[Lebanese President Michel] Aoun said the probe is divided into three parts. The first aims to determine the circumstances surrounding the cargo, the second where it came from and who shipped it and the third who was responsible for handling and securing it.
So the investigation involves everything up to blowing up the ammonium nitrate? Huh. That's fascinating:
Careful study of video of the blast shot from multiple angles and from multiple sources indicate there was not one but two separate explosions, about 30 seconds apart, and that the second explosion was definitely not from ammonium nitrate.
In addition, the narrative being pushed by Hezbollah and their toadies in the Lebanese government is mostly misinformation. The story told by the terrorists is that the ship originated in Georgia and was bound for Mozambique to drop off a couple of thousand tons of ammonium nitrate. It stopped in Lebanon and was prevented from leaving port for six years because the ship wasn’t seaworthy.
One big problem with that tall tale: the region in Georgia from which the ammonium nitrate was said to have originated has only been exporting it for three years.
Let's hope France can get the fourth part done.