Wow!
This is the time of year when things shift and move about with the cold weather. The Mid-Atlantic and Northeast regions have had a lot of ice and rain, which could have moved something out of alignment. All there needs to be is a slight kink on those rails, and the train will derail. If it isn't rail infrastructure, it could be a broken wheel, or something else that could have caused this including a brake system lockup, or stupidity on the crew's part by taking the curves too fast.