The film "Chappaquiddick" distorts a tragedy

[flotsam]

47. Nobody really knows...

...here's a different scenario:
A BBC Inside Story episode, "Chappaquiddick," broadcast on the 25th anniversary of Kopechne's death, advanced a theory that Kennedy and Kopechne had left the party in Kennedy's car, but when Kennedy saw an off-duty policeman in his patrol car, he got out of the car, fearing the political consequences of being discovered by the police late at night with an attractive woman. According to the theory, Kennedy then returned to the party, and Kopechne, unfamiliar both with the large car and the local area, drove the wrong way and crashed off the bridge. The episode argued that the explanation would account for Kennedy's lack of concern the next morning, as he was unaware of the crash, and for the forensic evidence of the injuries to Kopechne being inconsistent with her sitting in the passenger seat.[61]

Writer Jack Olsen had earlier advanced a similar theory in his book The Bridge at Chappaquiddick, published early in 1970. Olsen's book was the first full-length examination of the case. Olsen wrote that Kopechne's shorter height (she was 5 ft 2 in (1.57 m), a foot (30 cm) shorter than Kennedy) could have accounted for her possibly not even seeing the bridge, as she drove Kennedy's car over unfamiliar roads, at night, with no external lighting, after she had consumed several alcoholic drinks at the party both had attended. Olsen wrote that Kopechne normally drove a smaller Volkswagen model car, which was much lighter and easier to handle than Kennedy's larger Oldsmobile.[27]

For a deeper dive:https://en.wikipedia.org/wiki/Chappaquiddick_incident