My theory is that Lee Harvey Oswald was massively maladjusted and had a major inferiority complex. He spent his life trying to be important. He joined the military to make himself feel stronger, he tried to defect to the Soviet Union to make them pay attention to him, and then he tried to become a proponent for Cuba. When none of this brought him the fame he wanted, he decided to kill the president. And he did so successfully.
“When none of this brought him the fame he wanted, he decided to kill the president. And he did so successfully.”
You left out one step. He unsuccessfully tried to kill someone before the president, a major, or something.