[burnte]

Explain why they're different? Really? Why are mort and the other French word different? The why would take explaining the evolution of the language. The fact that they are different in itself is the point however. Dead is a very clinical word in describing the state of death, while deceased or "passed away" is a much softer way of communicating it. That's simply how English is. You can't look at it from the perspective of the French language any more the you can look at French via the lens of English. English is a mutt of a language, Germanic in origin, heavily influenced by Latin and Romance languages, with a significant independent evolution on its own.

The tone "dead" confers is much colder than deceased, which is exactly why the author chose to use it. To show the state couldn't care less.