It's pretty clear now what happened.
Assad was abandoned.
With Russia distracted by Ukraine, and Iran trying to manage its proxy war with Israel, Assad was not a priority.
Hezbullah, while having its military capability mostly intact, and its entire leadership reconstituted, did not want to get involved again in Syria. It would have been a political disaster as Lebanese people were in no mood to give further benefit of the doubt to Hezbullah.
Plus, with all the leaks and reports coming out, it seemed like Assad was not only deeply disliked, but was actively selling out Hezbullah, and Iran to Israeli intelligence, and Russia to US intelligence.
Basically, Assad played himself. He grew too confident, and tried to play all sides against each other. He underestimated his usefulness to everyone involved.
So he everyone abandoned him.