They removed the drive shafts (and who knows what else) for the flying part of the video, probably too heavy with them fitted.
(pause the video on the bit where you see a rear view on the track and there are clearly drive shafts and a diff)
The flying car always was and still is a daft idea, yeah you can build one but then what?, does anyone seriously think someone is gonna take something that expensive and flimsy into modern road traffic?
One bump and it'd be a write off even if repairable it would be under an airworthiness regulatory system,...so huge cost
Concept always was nonsense