Usually we see the aftermath of a pileup. Wreckage everywhere, ambulances, police cars, fire trucks, and a jackknifed truck or two. We don't normally see it as it happens. With this video you see everything, and it's nothing but chaos and panic.
It's also an instant story of people helping each other, doing their best to suss out what happened, and establishing some sense of order even as the dull thud of impacts and the crunching of metal continues in the background.
But I still wouldn't want to be caught in one, ever.