Fear will often freeze people. Also, he was 58, and it would take quite a bit of upper arm strength to pull yourself out, assuming there were no grippy surfaces for the hands or feet.
Yes I’m sure you are right. I hadn’t noticed his age—in the photo I took him for a younger man.
I was thinking that with the adrenaline burst a guy could almost high-jump out of the trackbed. But I would agree with you that the surprise of being down there (especially since he was pushed) and the shock of the train bearing down might have frozen him in place.