Idk how it is in Germany but my wife is currently trying to became a train driver in France and there are far more requirements that what you would imagine.
Even if the job is actually opened to basically everyone (and that’s pretty nice), you have to be in perfect physical and psychological shape with pretty strict tests, you have to be intellectually apt enough to follow the training which is pretty intense. You have to accept work conditions such as not knowing your work hours until the day before. You have to accept sleeping who knows where at least 2 times a week. You have to accept having only one weekend off per month.
So what happens is that when you have that much filters and you still want to hire train drivers, you can’t afford to expect your drivers to know another language on top of all of the rest.