They didn’t sacrifice themselves for random strangers; they sacrificed themselves for no one. I don’t hate sacrifices, but only when they make logical/narrative sense, like (spoiler) Klein’s sacrifice in LOTM.
Their sacrifice didn’t make sense there. Believe me, if they had stayed inside the ship to help maintain internal order and external security for MILLIONS of people, they would have saved far more lives than those supposed five.
Of course, there’s the whole moral dilemma about them taking away the opportunity from five innocent people, but even that doesn’t convince me. I mean, there are millions of people inside the ship, it’s unrealistic that they couldn’t handle five more.
Anyway, I barely even remember that part of the story anymore since I dropped that novel years ago. By the way, if you like western web novels, I recommend Mother of Learning to you. The protagonist’s morality in Learning is similar to Sunny’s in the sense that they try their best to save innocents, but it’s much less irritating and makes way more narrative sense.