Successive frames from this video are interesting.

The fireball wasn't the explosion.

Something flashed first, and then the fireball.

My guess is that the fire ignited a munition (stored in the warehouse by hezbollah), and then that set off the AN.

https://youtu.be/n-3GJwy6EI4?t=28

Ship circled in red is the Mero Star, that had just arrived the night before from a Ukrainian city on the Black Sea.

Supposedly it was unloading wheat at the time.

https://www.maritime-executive.com/article/16-detained-in-connection-with-beirut-explosion