Because the USA has a fundamentally broken healthcare system, which it propagandizes as the best in the world despite actual evidence that it is not.
300 to 600k per year salaries are not natural, German Physicians don't make that much or go to school for as long yet have similar outcomes.
In the U.S. it's 8 years of school plus a 3- to 7-year residency program, versus 6.5 years of school plus a 5- to 6-year residency program in Germany.
This is just another example of the US being a place where the gap between the haves and have nots is extremely large.