Why did Billy Grey die in grand theft auto iv the lost and damned?

Billy Grey dies in "Grand Theft Auto IV: The Lost and Damned" due to a power struggle and betrayal within the Lost motorcycle club. As the former president, his reckless actions and drug abuse alienate him from the other members, particularly Johnny Klebitz, who ultimately decides to confront him. In a climactic confrontation, Johnny kills Billy, marking a significant turning point in the game's narrative and Johnny's character arc.