Because SUSE is a German company

Suse is a german company and therefore Suse Linux has some improvements for german users. And if you're doing it to get away from american companies to get your own sovereign OS, that totally makes sense. Better localization and from your country. And the support might also be in German

Governments want a stable distro, which has great general support and the option of hiring developers for additional features. If something breaks government workers can not do their jobs, so it costs money anyway. So having professional people behind it, who can be talked and fix the problem quickly is something a government really wants. In addition to that, they require some niche features, which need to be developed. In other words, they really want a stable distro with a professional team behind it and as it happens Suse is the only such company in Germany. Even better they already have experience in dealing with government agencies and well speak German. The alternatives would be CentOS or Fedora from RedHead or Ubuntu from Canonical. However those are not German or European.

Because it's European Based, and I guess they won't bother to test and approve multiple Distros for a single state