I think for plot/writing reasons (similar to The Martian), Grace’s crew died. I wish there was a bigger deal made about the mysterious sleep deaths too, mostly because story-wise it’s a great character beat/world-building piece for Rocky as it’d be horrifying for him in context.
The explosion deaths are also pretty convenient to leave Grace on his own, show that stupid crazy terrible things happen as per the style of disaster stories, and more to show the contrast between actually very competent ideal candidates and Grace himself (again setting up his predicament).
Sirens of Titan by Kurt Vonnegut
I was a God-fearing thirteen year old scared of burning in hell for all eternity, but after reading that book, I just thought about how there was already enough absurd suffering, that worshipping any deity was less important and less impactful than just being kind.