Another possible factor (but hopefully not connected) is that local news in Philly is reporting that "moments" before the Amtrak crash a SEPTA train was "disabled" by a projectile that so damaged the engineer's "window" that the train had to be stopped and all passengers disembarked and put on busses.

Wondering whether something could have happened to the Amtrak engineer. I know from my long-ago rail employment that rocks and gunshots directed at engines are not uncommon. It may be a lot worse now than it was back when I was working on a railroad on the west coast. I recall seeing photos way back then of Boston-area locomotives with heavy screening over the windshields.