What is the reason for a person's piety, good intention, and resolve to disappear, and what is the reason for a putrid wind to be emitted from his body while he is still alive?

There is nothing specific regarding the reason for this matter. It is advised for a person to be mindful of God's observation, adhere to the religion, commit to acts of obedience, and maintain cleanliness and use perfumes; for obedience to Allah and His piety are a means of achieving all aspirations. Allah Almighty said: "And fear Allah that you may succeed," and He Almighty said: "Whoever does righteousness, whether male or female, while he is a believer - We will surely cause him to live a good life, and We will surely give them their reward [in the Hereafter] according to the best of what they used to do."