Flatbed tow truck brake failure on incline - GIF

[Frank S]

I don't think the brakes failed as much as there was too much weight transferred to the stabilizer. that steel bar would not offer as much resistance to slippage like the tires would. But it makes me wonder why the tow truck driver wouldn't have placed chalk blocks behind the tires before starting the recovery

[Rangi]

Is that locally obtained chock under the rear wheel?