Focusing on the direct cause of the blast is a huge distraction from understanding why the 2,750 tons of ammonium nitrate were stored in the middle of Beirut for 7 years.
The president Aoun and his senior leadership were all aware of this problem but said they didn't have the authority to do anything about it. IMO, this is a hilariously bad argument that's deflecting who the most likely owner is. Aoun and his lackeys apparently have the authority to start a state of emergency and shoot protesters but don't have any such authority to prevent half of Beirut from being nuked.
The director of the Beirut port Badri Daher has been running bazaar ever since he's been in that position, regularly stealing supplies from shipments, suing reporters for defamation and beating up investigative journalists. The port director also reports to the Amal party which is closely allied to Aouns.