He chose the latter and left the entire army section to his allies (Russia and Iran). While Russia was busy with Ukraine and Iran isn't any good at anything, he had no choice but to give up and leave,
A decade ago when he only had control of about 16% of Syria, he officially requested Iran's help and it was only then that the tables turned and it was Iran that defeated the ISIS-US coalition. The only reason why Russia is there is also because Iran convinced them to bring their airforce to counter the US airforce that was providing ISIS with air support.
Recently, the same Arab dictators who kicked him out of their Arab "league" many years ago started fooling him with fake promises under one condition: to kick Iran out.
FYI Iran left Syria a while ago. That is why Erdogan saw the opportunity to invade at this point, he knew the only force capable of keeping his terrorists out was gone. Otherwise if the Resistance ground forces where there, these terrorists who mostly had light weapons and were on the back of pickup trucks driving on open highways wouldn't have been able to get past Idlib.
In any case, you are right that those celebrating are fools. We are already seeing how Israeli terrorists are advancing from the west occupying more of Syrian soil, expanding their own occupied territories. All that there is constant bombardment of all Syrian infrastructure...
Meanwhile Turkish al-Qaeda terrorists are sacking the cities.