Headcanon:
Mello is often manic and is prone to magical thinking and a few full out delusions, which generally work for him. However one of these delusions is that he doesn’t believe he can die, which was helpful to get him where he ended up, but was partially why he actually ended up dying. He’s smart enough however that he only ever shared shared this once, with a low level grunt when he first was trying to get involved with the Mafia.
“You’re going to kill yourself little man”
“I can’t die.”
The man was taken aback by this.
“Son don’t say stupid things like that”
Wide wild eyes
“Then kill me"
Due to that, in combination with Mello’s strange and obviously invented name, the man thought the kid was mental and on a path to get himself killed, and did everything he could to keep him out of the mafia. On finding this out Mello manipulated another man to kill the guy like the calloused, emotionally unhealthy and unstable individual he was at the time
