Without reading the article (site is down) my expectation is that the data will show significantly lower salaries in Europe than in the USA.
One of the explanations is that there are almost no genuine software development companies in Europe. Software jobs there are mostly internal (enterprise) software development or customization, and not software product or service development.
Being a cost centre instead of a profit centre has its effect on salaries, and is hard to overcome. If you are not satisfied with your enterprise developer role in the USA, you go to FAANG or one of the numerous startups. In Europe, you go, where? In another company that is not different from previous one.
One of the explanations is that there are almost no genuine software development companies in Europe. Software jobs there are mostly internal (enterprise) software development or customization, and not software product or service development.
Being a cost centre instead of a profit centre has its effect on salaries, and is hard to overcome. If you are not satisfied with your enterprise developer role in the USA, you go to FAANG or one of the numerous startups. In Europe, you go, where? In another company that is not different from previous one.