What I can piece together post the Lebanon war, Saudi Arabia and other gulf states provided substantial aid to Lebanon to reconstruct. But in 2016 Saudi Arabia cut off its aid when relations got spoiled. Lebanon has lots of government corruption so much of aid was wasted. Then there is the explosion last year that set them back even more. Foreign countries want reforms before they will donate further.
https://en.wikipedia.org/wiki/Lebanon%E2%80%93Saudi_Arabia_r...
https://carnegie-mec.org/2020/06/09/lebanon-not-expecting-gu...