As for size, larger vehicles/SUVs are fairly popular in the UK, probably in part due to the deteriorating state of the roads (potholes, speed bumps)...
And the head of the car safety organisation strongly implied it wouldn't be street legal. [2]
[1] https://www.drive.com.au/news/tesla-cybertruck-pulled-from-s...
[2] https://thedriven.io/2019/11/27/tesla-cybertruck-may-be-unsa...
And while I agree that the Cybertruck doesn't seem like a safe vehicle at first glance, Tesla's track record on passive/active safety should be enough to stave off any premature jumping to conclusions prior to the release of real test data.
Also this quote was quite odd: “We’ve got a concern that Tesla is very interested in the occupants of the vehicle, but it can’t ignore the other road users as well.” This is a hideously disingenuous comment for the head of ANCAP to be making about a manufacturer that makes one of the safest cars on Australian roads. They seriously have "a concern" about the maker of vehicles which score extremely highly overall, and which matched or exceeded an equivalent Volvo EV in every category[0][1]?
[0] https://www.ancap.com.au/safety-ratings/tesla/model-y/726c22
[1] https://www.ancap.com.au/safety-ratings/volvo/c40-recharge/f...