Quite common if they are hiring in bulk
Unfortunately, this is a common situation with some companies, not only in Germany but elsewhere. To put it simple, company is usually well known, and reputable in its field. Think Mercedes-Benz or Bosch. They do not have to be that big, but is expected from candidates to already know about them (unless they were living under rock :) ) . Especially in Germany, such company would provide certain job security (due to labor laws they cannot just fire you) and would be a nice point in the resume (he worked for BMW ) .
Therefore, it is expected from candidates to be honored to work in such company, and grateful if given a chance. Also it is expected that for each position there will be a lot of candidates, especially if the company is hiring in bulk for more junior positions. For example, such company may decide to hire 30 embedded software engineers straight from recent university graduates. For these positions they could have hundreds of applications, especially if they allow foreign citizens to apply. In such situations they are not looking for primadonnas, they just need sufficiently skilled individuals they could mold into what they need. Certain obedience and lack of individualism is unfortunately expected. Or in simple terms, successful candidates would need to fit into corporate culture.
Usually, there would be several interviewing teams and several rounds of interviews, each with strictly divided roles. They would go for efficiency, trying to filter out unsuitable candidates as fast as possible. In lot of cases candidates would not compete for a certain position in a certain team. Instead, they would assign them to specific duties only after the hiring process is completed. Therefore, interviewers would sometimes not even know specifics of the job.
As a final note, sometimes these practices do carry over even when hiring more senior people, simply because of large bureaucracy and overblown role of HR. Of course, this puts off some (lot) of people, so they do not always get best candidates for the job. Since this companies usually have good position on the market and lots of money, pressure to change is small (until is to late :) ) . Therefore, as an advice, if you do not like such corporate culture do not apply. Of course, usually there is enough people that would go on even with these inconveniences, simply to have good salary, nice tick in resume and job security.