“how the heck does an army with an air force lose to one without an air force?”
Simple: the Syrians have lost planes, pilots, airfields, have too few planes, spare parts and pilots. They also are fighting an enemy which is so low level, and so rarely masses troops, that it is hard to harm from the air. Remember, we have an air force too, and we’re not really hurting ISIS that much either - and our air capabilities vastly outpace those of Syria.
And the Syrians probably don’t have good aerial bombs, that is why it is said Barrel Bombs have been used in Syria and Iraq.
That's because our pilots aren't being allowed to hit anything.
And the number of our airstrikes is way low daily, no more than 20.