I think there are several issues in play here:
Is naked survival the only goal? The ones who surrendered were not treated nicely by any measure of the imagination.
Depends on the conqueror. Khan, despite his reputation, was aware of the maxim. "Dead men pay no tribute." History, as a whole, would be much different if the serfs and so on resisted to the last man against conquerors since most of history has 99% of humanity paying tribute lest they be killed or enslaved.
It's also a form of the Prisoner's Dilemma. Genghis Khan (like many rulers across history) gambled that not enough people would resist versus submission to make a difference. 14 City-States, all of them resist, it's a victory. 1 resists, it's destroyed. So who is going to resist without guarantee of the others?
If you surrender, the Khan might be overthrown the next year or die or you might join up with the Horde (which is how he and Saladin ran things--the latter conquering all of the Middle East by having one conquest pay for the next). The next Khan might be better too.
Death for you and your family...is very eternal.
The ones who resisted assumed they had a chance of victory. It was a gamble they lost; but, if won, it would mean freedom and relative quality of life over de facto slavery.
Which is a point why weighing your options works well.
"The Corbomite Manuever" is one of my favorite "Space Battles" in Star Trek (baby at the end aside) because it shows everyone being a rationale actor. They don't know the other, they are both posturing because they don't want to show weakness, and neither side is a bad person. They could go in phasers firing but that would just get everyone (possibly) killed. It's pro-peace but it's peace by making sure that the other side is aware the other isn't a target either.