The inhabitants of Damascus were put to great confusion. What should they do? The armies of the Tatars would attack them within a few days. It was the habit of the Tatars to ruin everything, and the people of Damascus had not been formerly trained in Jihaad, and were short of fighting skills. The professional soldiers and commanders ran away and left their bastions.
The situation was extremely degrading.

The elite and notable men of Damascus met and unanimously decided to do the same as those of Hama, i.e. to hand over the keys of the city to Hulagu, in return for security. No one disagreed with this opinion but a few Mujaahids who decided to hold fast to the castle of Damascus and defend the city to the end.
Hulagu was right in his assumption when he granted real security to those of Hama, which led the inhabitants of other large cities to do the same.
A delegate of the elite of Damascus went out to receive the army of Hulagu and hand over the city keys to him.

https://en.islamstory.com/index.php/en/artical/20820/surrender-of-damascus