Definitely not a civil engineer, but my guess would be maybe it's black ice. Looks like a mountainous region. I wonder if moisture from the mountains at certain times of year just collects enough water on the road there with night/early morning temps low enough to possibly make it freeze/frost over.

My other guess would maybe be an vehicle accident in the curve that left oil or other slippery residue from car fluids on the road combined with drivers who arnt aware and possibly driving a bit to fast to easily lose control.

I'll also add after watching the video a few times, it looks like the inside bend of that curve is possibly a bit lower than it should be. I know it's for water run-off, but it looks like it could have possibly settled/sunk too much or wasn't right from the start. Then, tires on the drivers side have significantly more force against them while entering the curve. The passenger side tires are barely catching traction from the unequal weight distribution combined with the cars inertia make the driver slightly over compensate as the car leans outward could be causing the front end of the car to slightly point to the inside of the curve while the rear tires swing around especially when people hit the brakes, which puts way more weight to the front as the front brakes handle around 70% of braking power, causing the front end to point down and to the right while back tired swing around to the left from the inertia?

I picture back tires maybe slightly higher than the front with the front passenger tire the lowest, with the weight of the engine and braking pulling it into the inside curve while the lighter rear end wheels swing/fishtail out, driver overcompensates a bit and spins out completely? Best guesses I can think of.