My hypothesis #1: Something on the track engineer saw and started to slow but still hit. Hit caused bumping and jarring that broke hitch, momentum allowed back car to stay close enough after hitch broke and engine continued breaking to allow air hoses to stay connected.
My hypothesis #2: Engineer was sufficiently alert that at the first sign/sound/jarring of a problem he immediately started breaking and allowed back car to stay sufficiently close.
Breaking or braking? They are two different things.
A surprisingly high percentage of AMTRAK trains hit things. I’ve been stuck for hours many times in the middle of nowhere. When it’s very bad, I’ve seen our car attendant hide. I believe the rule is that they stay until they find the head. I’ve never understood people who would lay the moral pain of their suicide on another human being, as they do with train engineers.