I omitted to add, you have still not explained why hardly a Syrian was willing to defend the Assad regime. Hardly a vote of confidence.
Well what exactly happened is still murky, but it appears at this point, with what limited knowledge I have, that Syrian military leadership was bought off by foreign money and told troops to retreat. With the sanctions and theft of Syrian oil by the US there was no money to pay them so they resorted to corruption, theft and receiving bribes. I read that they were only getting paid $7, but it wasn't made clear if that was per day, week, or month.
Also from what I understand, most of the army was conscripts, so without leadership telling them what to do, an effective defense was not going to happen.
There were reports that Iran and Hezbollah offered to send troops, but Assad turned them down, for what reasons is not clear. IMO when Russia and Iran saw what was going on, they cut their losses and decided they were not going to fight if Syria wasn't going to.
So things quickly collapsed. However, thousands of Syrian soldiers fled to Iraq, have reorganized and the last I saw were being bused back into Syria in green buses lol to form a resistance.