The group that has captured Damascus, HTS, is not actually "the same group" as Al Qaeda, though their leader was once part of ISIS, Islamic State in Syria, which is related to Al Qaeda, and both groups are clearly Islamist. More importantly, HST is currently allied to several other groups including the Syrian National Army who appear to be more nationalist than Islamist. The US appears to have been bombing ISIS to make sure they didn't get to Damascus first.

Who are the Syrian rebels who have captured Damascus

Time will tell what sort of government will emerge.