I think this comes down to giant game of international chicken. The only reason assad is still viable because Russia made clear that their national interest is keep the current syrian government power. If it was not for Russia we would have total choas in syria, every faction with a stake would fighing each other (I will concede that is already in situation that could be called unsettled currnetly).
If Assad falls then syria will destroyed as a political entity and be balkanized. I think a united syria is good thing for the stability of the region.
The Syrian Arab Army supports Assad, they have laid down their lives to defend their country, and, still, they would not have survived without the able assistance of: Hezbollah, the Iranian military, and the Russian AF.
So you are quite wrong to idenfity only the Russian AF. It is also disgustingly disrespectful to those who have given their lives to defend their country.
Lets be honest here the only thing that keeps the jackals at bay is Russia. If the Russians walked away this whole thing would collaspe in months.
I remember when the whole chemicals incident happen and syria gave up its chemical weapons. It was Russia that blunted the momentum to attack by the Western powers. The whole Saddam playbook was ready to go, new hilter, weapons of mass destruction, threat to its neighbours(gulf cartel), Isreal ready to annex the Golan heights, Turkey and Edergoans dream of a new ottoman empire, neutralize a ally of Iran. At that point the country would torn apart. Russia stopped that plan. Iran and Lebonan contribtion was worth big doughnut.
Today we have the whole bombing allepo war crimes thing. Again the only thing keeps the west at bay is Russia. Washington is looking at its possible actions right now. I think they have concluded that russia will defend its interests and thats makes things too costly for washington.
What these things have in common is that these are modern cases for casas belli. But russia is saying no. The russians are not dieing for Syria they laeve to the Iranians, Syria, and Shia allies. But what Russia does is provides a very height barrier to engage in regime change. Russia most important contribtion is that they provide political power. The power players that want to tear apart Syria. They not flying to Iran, or Lebanon to discuss the future of Syria. They are talking to Russia asking, bribing, bullying to stop it from supporting Syria. This should be a clue as who decides the fate Syria.
I cannot agree with this naiive remark. "Accidents" happen all the time. The US, along with its NATO and other supplicants [Denmark, UK, and Australia] "accidently" bombed the SAA for an hour, killing 62 and wounding 100 soldiers. The Daesh and other terrorists had moved in, coordinating with the US, and took over the space once the US stopped their bombing. Perfect timing. Some "accident".
When the US bombed Yugoslavia in the 1990's, they "accidently" bombed the Chinese Embassy, killing Chinese nationals. IMHO, this was not an "accident". It was a warning.
If a country carries out an enormous military build-up, flys sorties along the border of countries far away from its own borders, turns the transponders of their aircraft off and tests the defences of its rivals, funds, trains, helps and supervises terrorists that attack other countries, then an "accident" is simply part of the overall plan.
Perhaps I should provide greater distinction to my comment. Syrias future without Russia would be choas and dismemberment. As to US openly starting www 3 over syria and planning to attack Russia as a policy is nonsense. The US wants cheap and quick wars and niegther apply to russia. Both these countries can reach thier respective homelands with weapons, I personally don't think US can subdue Russia. Even if by some miracle the US had presence on the ground in proper Russia and threaten the existence of the state Russia will always have nuclear weapons. Plus China would interven if the Russians were on the ropes, China knows that its next if Russia is neutralized. Why would US risk this on the fate of Syria.