If you look at their stock performance and management compensation the last 25 years, much of the responsibility seems to lie with the manufacturers themselves.
They had roughly two decades to adapt, but instead they often relied on strategies like pressuring German workers with the possibility of relocating production to Poland to keep wages down, while investing little in research and development during a period when sales were strong and new markets, such as China, were opening up.
There must be more to it. German automakers did belong to the top 10 (for some periods even top 5) R&D spenders world-wide. It seems they just did not spend it wisely. Similarly, the claim they "kept wages down" seems to require some nuance. VW workers are known to be very well paid. From the outside it seems like these companies became large behemoths who were not able to spend their R&D money wisely and their outsized pay packages forcing them to offer their products at uncompetitive prices.