“The Great Gatsby” is about death, which is inevitable. This includes the death of people and dreams.
Although no one knows when they are going to die, I think that without the desire to gain more money and power, both Gatsby and Myrtle would not have to die like that. As a consequence of Myrtle’s death, Gatsby get killed by George. Throughout Gatsby’s life, I do not think that his money has made him a successful and powerful man. By having him dead at the end might be a way of showing the end to his dream and desire. For example, he only thinks about being with Daisy and nothing else. Therefore, after Daisy goes away with Tom, there would be no other reasons why Gatsby should live.
Gatsby’s dream is to be reunited with Daisy. He believes that he can “buy” Daisy back:
“Can’t repeat the past? …Why of course you can!” Although having an affair is not the right thing to do, Gatsby did it just to fulfill his dream of being with Daisy. His dream is obviously ruined when his car hits Myrtle and it disappears when he dies.
Myrtle wants to improve her living by having an affair with Tom, who can give her much more money than her husband. Her dream is destroyed, as Tom does not care about her.