He tries to think about something complicated. Leareth, supposedly, talked the Yeerks into letting him go by appealing to their better natures. It feels - absurdly improbable. But the situation they're in feels improbable too. He thought he'd have to destroy every pool to get the Yeerks to admit they'd lost. And then there'd still be the risk backup from off-planet would arrive in time. And - there are probably a lot of elements to realizing you don't want a war. Realizing you would lose it. Realizing you're outmatched. Realizing that the best-case scenario is the destruction of the planet.
Realizing that your enemies are people, maybe.
Probably Andalites are no more people to Yeerks than Yeerks are to Andalites, excluding the one Yeerk who took an Andalite host. Probably some of them were thinking of the enemy with the same uncomplicated hatred that plenty of his people feel, and it was - genuinely valuable to learn that the Andalites were considering how not to destroy them once the war was won. Something he was only considering because of Leareth and Vanyel.
<Nine.>