Odo curing the Link is never stated to be a condition of surrender. The facts we have are that she agrees to stand trial, and that Odo intends to rejoin the Great Link. But the two are not explicitly linked (no pun intended) as though one equals the other. I have no doubt it played a part, but nothing in the dialogue shows it to be the reason.
Well, the dialogue skips over THE reason entirely, so by that logic you simply can't say why she chose to surrender. But it does explicitly link Odo's return to his people with curing them, so...
Also, there is this:
ROSS: Four hundred years ago, a victorious general spoke the following words at the end of another costly war. Today the guns are silent. A great tragedy has ended. We have known the bitterness of defeat and the exultation of triumph. From both we have learned there can be no going back. We must go forward to preserve in peace what we've won in war.
(Douglas McArthur, WW2. The Founder is escorted from the table.)
FOUNDER: It's up to you now, Odo.
and
KIRA: You could come back, you know, once you've cured your people.
ODO: I could.
KIRA: But you're not going to do that.
ODO: Nerys. You know my feelings for you will never change, but I have to do this. My people need me. They need to know what I know, to learn what I've learned from living among solids. It's the only way they'll ever learn to trust you.
Which I'd say strongly implies that the Founders will not just accept Odo's presence as a fair trade for ending the war. They're going to have to be convinced not to keep up their hostilities with the AQ. Because Odo is not actually more important to them.