Questions on the Syrian rebel advance

The flare-up in the Syrian war has shaken an already unsteady region. At this point, without evidence, it is impossible to know whether the Islamist rebels of Hayat Tahrir al-Sham (HTS) acted on their own, seeing the weakness of the regime's allies Russia and Iran, to take a large chunk of territory that includes Aleppo, or whether foreign powers pushed them to do so. Who gains and who loses from these latest developments?

The rebels themselves are certain winners, taking over Syria's second city and erstwhile economic center, projecting the image of a victorious force. The government is just as clearly a loser, revealing how it could not build something stable on the ruins of the city which it retook in 2016 after intensive Russian aerial bombardment and the mass slaughter of citizens. Russia and Iran, too, are losers, obviously unprepared for the recent action in a region...