Original sentence: Kennedy would be first of a dynasty in the White House, but these predictions were not borne out, and the idea  largely dropped off the public's radar after Edward Kennedy was invlolved in a drunk-driving incident (in which a passenger in his car was killed) in 1969 and Robert Kennedy was assassinated in 1972
Edited sentence: Kennedy would be first of a dynasty in the White House, but that did not occur after Robert Kennedy was assassinated