Works similarly in Germany, with the difference that 4.0 is the lowest passing grade and 1.0 is the highest.

See https://en.wikipedia.org/wiki/Academic_grading_in_Germany

I don't see how one professor makes the entire program.

FWIW I did my masters there and in my opinion the way they evaluate students is suboptimal anyway - but I don't know if that's a TUM thing or a German thing.

He doesn't; I just gave the example of one course but the pattern happend for other courses, too.