That isekai setting was rather too shoehorned, given the "i know modern medical facts" isekai clergyman that appeared. Still, looks like the author really wanted to bring out a message, so he also used the popular trend as a means.
Author haet smokers, that' just it. Which makes me wonder why "smoking a pack of cigarettes every hour until you bite it" isn't the prime method of Death Penalty yet.
On the other hand, there are people who were able to live their life to their possible fullest despite getting betrayed by their very own body and health.
The moral of the story: DON'T WASTE IT.