I am no different from any of the other locals, these Germans, who are on the same night train coach as I am and are sleeping..no big deal at all. If they can do it, presumably, why can't I?
It's got nothing to do with being German or whatever. It's got everything to do with how you're built, your tolerance for noise, motion, and other factors.
My spouse can sleep standing up, with noise, movement, other things. Sleeping on a train for her is a non-issue. Me, I can't sleep at all if I'm not in a quiet, dark, perfectly still place. I can't even sleep on a ship - a big, ocean going one - because of the motion and the vibrations I can feel coming through the ship's structure (I once was awake for 36 hours coming back from Alaska on a ship). A train? Fuggedaboudit. People are built different. Some of us can sleep under challenging conditions (lucky you) some of us can't, period. Whether or not night trains work for you depends on which bucket you fall into.
A corollary: some people are prone to motion sickness, some are not. My spouse gets sick easily in cars, buses, ships, airplanes, etc. She has gotten sick a few times when I drive her to the corner grocery store, just blocks away. OTOH, while she turns green and blows chunks on small aircraft, I love turbulence. I've been on small boats where everyone around me was doing the technicolor yawn continuously for hours, while I sat there happy as a clam, wishing I could eat some squid tacos. Everyone's different. Just because you can sleep on a train (or tolerate aerobatic flight maneuvers) doesn't mean they next guy/gal can.