You don't take thinking or thinking people seriously so I'm absolutely not surprised, and we are done now. When asked to think for yourself cannot. All you can do is post what others say.
Common sense tells me Mary Jo was drunk. Drunk enough that she left without her purse or her hotel key. A woman doesn’t go anywhere without her purse. She certainly would not go have sex on the beach without her hairbrush or makeup bag to touch up afterwards. And she would not have been driving without her drivers license which was in her purse.
She wasn’t planning on driving so she wouldn't have been watching how much she drank at the party. Ted was planning on driving so he would have been more careful about how much he drank. Also, it was his car. Why would he allow her to drive his car, especially since he was familiar with the roads around the island and she wasn’t?
If she was drunk or passed out in the car, this could be a factor in why she died. If her head hit the window, or the roof and she was knocked unconscious, this could be a factor in why she died.
It’s unlikely either of them were wearing seat belts since it was only 1968 when a law was passed making them mandatory in new cars. Nobody wore seat belts back then.
In your scenario, the steering wheel would have killed him on impact but that would depend on the height of the fall - a 35 foot fall would have been very survivable especially if he slid across the seat to the passenger side as the car went off the side of the bridge.
The only reason you can come up with is that he lived and she died so he could not have been in the car. If that were the case why did he say he was driving? What benefit was it to Kennedy to say he was? There isn’t any good reason for him to say he was driving unless he was.
The more likely scenario is that he went back to his hotel to try and figure some way to worm his way out of the mess he was in. To come up with a plausible lie to save his political career. That’s the common sense answer to why he waited so long to report the accident. Seeing no way out, he went to the police and told them he drove off that bridge in the dark and the girl died.
As for the rest of his story, who knows how much is true but nobody who was at that party has said anything different in all these years so maybe it was.
Letting him swim back to the mainland just defies logic and reason though. Maybe he was hoping to drown and not have to face what he’d done.