… the government of President Bashar al-Assad had no wish to change and that there was no immediate prospect for a diplomatic breakthrough.”
That’s because if they do, they’re dead. Syria is a majority (71%) Sunni Muslim country but the Assads and the rest of the ruling class are a minority (11.0%) Alwai Shia. In case you haven’t been keeping track, Sunni and Shia get along about as well as Protestants and Catholics did during the reformation. If you imagine a 16th century country that was 71% Protestant ruled by a 11% Catholic nobility (or vice versa) you get the picture of the religious dynamics.
It doesn’t help at all that the Assads and the rest of the Shia have been both inept and brutal towards the majority Sunni for the last 90+ years. Most Sunni are very, very poor and most Alwai Shia are very rich in comparison. The Assads and collateral families are very wealthy.
The Assads have kept power to date solely by using Israel as the evil outsider to give common cause between Sunni and Shia. That is why Syria has long maintained such bizarre stances on negotiating with Israel e.g. “give up back the Golan Heights artillery positions we used to shoot at you from first and maybe, just maybe, we’ll negotiate.” The biggest disaster they could imagine until recently would be if Israel suddenly disappeared.
Now, the people of Syria have gotten so hungry that they don’t give a damn about Israel. In any case, Israeli raids against what most people assume where Syrian/Iranian WMD sites of some kind caused the Assads to loose serious face in the eyes of the people. The Sunni majority may feel they can give Israel a good kick as well as the Assads.
Serious religious friction, brutality and oppression, and systematic looting of the people has made the majority of Syrians very, very angry. Many ordinary Syrians have suffered so they have every right to blood vengeance and they will take it they get the chance.
For the Assads, there is no negotiated end. They saw how quickly Gaddafi’s regime disintegrated and how he died at the hands of his own people. If the Assads’ grip on power slips even a bit, they’re dead. The Assads know full well that they are riding a tiger they can’t jump off of without being eaten.
This isn’t going to end well for somebody.