Around Germany and Greece there were other countries. They went by names like frugal four and PIIGS. They forced "austerity" and stricter working hours onto indebted countries to save their own banks.
The colours on this map show well that northern "productivity" is not about working hours, but about other topics that did not get addressed. Among these topics are also tax heavens (think the Netherlands) and money laundering (think Austria's special relationship with Russia).
So it was nothing more than poor political leadership without vision.
The automotive industry is why Germany has such a bad time economicly speaking. At least in the last five years or so. Car sales in the Europe(EU, UK &EFTA) were 15,805,752 in 2019 and only 12,963,614 in 2024. Obviously car manufacturers prefer cheaper factories in eastern Europe over the more expensive German ones, hence you see them shrinking staff. For the suppliers it is even worse, as a lot of them are specialized in combustion engines. With BEVs doing what they do, that means mass layoffs. That is why German automotive industry only employees 761,000 workers today. In 2018 it was 834,000.
At the same time Germany is able to do much more then just automotive and those sectors are able to grow. Hence you see stagnation.