Syria is 74% Sunni Muslim.
Assad is an Alewite which is a Shia sect of Islam.
The Alewites and Shias (Assad’s power base) are outnumbered 4 to 1.
Trust that Assad populated the the officer corp (certainly the pilots) with Alewites and Shia. He would NOT want a disgruntal Sunni pilot dropping a bomb on his palace or defecting with a fighter jet.
So, we can assume Assad’s infantry was majority Sunni. They have long since deserted or otherwise have no interest dying for Assad.
You CAN NOT take back and hold territory with air strikes, tanks or artillery strikes unless you have infantry to occupy the territory.
Putin’s Chechen ally (former warlord) is wanting Putin to allow him to put troops on the ground in Syria.