Funny you ask that, because people in Germany's software sector are about the least organized ones.
(German) https://www.heise.de/newsticker/meldung/Viel-Arbeit-wenig-Mi...
Also, there is nothing special about software developers in Germany. They don't fare any worse than other technical staff. The biggest predictor for pay is the size of the company.
Having worked in the US for almost a decade, having seen a lot of different software companies because of my role, and now, long back in Germany, working for a new software company that I own a sizable part of (co-founded between "veterans" of the software industry), and looking at my country with new eyes after coming back from the US (and it took me quite a few years to come to the conclusions):
It seems obvious to me (now) that overall the US is quite a bit richer than Germany (questions about wealth distribution, inefficient health care, and education notwithstanding).
Software in particular is not exactly a strong suit of my country. We don't have the scale, we don't have the investments, we don't have the expertise (comparing the levels between US and Germany), we don't have the same kind of market outlooks to justify similar wages.
That last bit is just my own conclusion based on my own thoughts and observations, I did not study the subject. Even just walking around in what are supposed to be the best parts of my big city, after having seen much of the US where I traveled a lot and looked at many places and neighborhoods because I really liked exploring them, I am damn sure US "wealthy" is on another level to German wealth. I'm not looking at the top 1%, but top third or quarter. Below that it's harder to say, and when including questions of safety net or health the comparison is different - but we were talking about well-paid software engineers.
In my opinion, we (Germans) are not nearly in as good a position as we think or are told about ourselves. I think software engineers (and engineers in generell) simply can't be paid that much more here. It's not that all the money goes to somebody else, it's not there to begin with.
For example, the EU and the US as a market are not comparable. It is much easier to sell to all of the US than to even sell to just a few countries within the EU. It may be not too hard legally and logistically, but culturally the EU countries really are completely different countries. Germany is not exactly known as an exporter of software either, apart from SAP.