Perhaps unlike Germany, in the US, people in those positions will not be able to come close to earning what they earn if they leave. Probably only half at best. A medical cert doesn't translate to much else besides the cert.
So like you mentioned, it's very difficult and grueling work, and people (in the US at least) get trapped because of the money. Passionless souls doing something they hate because they'll lose their upscale home and Mercedes if they quit.
I doubt that they hate what they do, it's just the shitty working conditions that render you unempathic and cynical.
Most of them care very much about what they do, and give everything they can for the patients. Otherwise they would have quit a long time ago. (I've had to do a 3-month nursing internship as part of my medical studies, it's mandatory in Germany)
Better staffing makes a day and night difference. I've experienced it first-hand as a doctor. The more overworked you are, the more cynical and unempathic you get.
After a weekend or some time off, it's already much better
In other countries with better staffing (Switzerland or Austria), it's a also very noticeable how much better the mood and morale is of the staff.
Nurses in Germany could never afford a Mercedes or an upscale home, but they would also probably make less, switching jobs. It's not that they don't love their job, they just can't take it anymore. You also rarely see old nurses for that reason.