Aren'tcha glad you ain't this poor SOB

Looks like the plow hit something that triggered the springs
(Can't think of the name, but its a safety mechanism that flips the plow down like you saw, when it hits an "immovable object")
Guess the driver didn't know how to react to that

On the bright side, this turned the plow blade into a moving speed bump, much less dangerous then hitting it face on