It's stupid, but they've got their feet on the pedals, the road looks empty, the seatbelt is fastened and there's a passenger to take the cat when the road situation changes. And they've got an autopilot AI that can kind of deal with well marked and empty roads. The conditions are ideal for this kind of stunt.

The only danger is that the cat has no safe place to sit once the video is over. It's a cat and it might do something stupid like injure the driver or jump on the dashboard.

Driving with loose animals is insane, but people do that all the time and it's not what you seem to be complaining about? You seem to think that the driver won't be able to swerve if an object materialises out of nowhere (only thing he can't control quickly is the steering wheel), but swerving with a loose cat wouldn't be a good idea anyway.