Bottom line IMO is he "boiled" the brake fluid from riding the brake pedal. Brake fluid in common hydraulic brake systems doesn't circulate so the pockets of brake fluid that pushes the caliper pistons is the first to fail and turn from a liquid to a gas. At that point the brake pedal goes right to the floor just as you can hear in the video. You can pump all you want but they are done. The brakes would have been fine for the most part had the driver not used them (riding the brake pedal) to control a vehicle with a sticking throttle......dumb @$$, Brakes take kinetic energy and convert it to heat energy and most brake systems can dissipate that heat energy without boiling the non-circulating brake fluid. Too much heat energy from riding the brakes and fail. I could get a rear brake disc and metallic sintered brake pads glowing in less than a minute on the dyno and the brake pedal would drop (no pedal pressure) and in most cases the brake line would start to melt and disconnect from the banjo fitting where it attached to the caliper. The guys in the race shop wouldn't believe me so the bets were on.................yep less than a minute to fail by riding the brake pedal.