It’s simple – if the energy of the crash goes through the drivers body, that body can’t take too much force, hence driver dies.
I personally think Kimi will stay at Lotus and Ricciardo will step up to full Red Bull. As daft as it sounds, I also think Massa will step aside for Grosjean at Ferrari. I would have said DiResta but he has become a prima-donna this season – and thats saying something in the world of F1.