What you can read about the topic in Germany is that the switch had a lot of ideology behind it and after more than 13 years people are still unhappy.

You have to consider this is an administration of one of the largest cities in Germany with lot's of custom processes and tools. Also workers there vary from their IT background and I guess most are not power users.

Their approach was basically eliminate Windows everywhere and tell everyone Linux is better.

They even gave everyone notebooks with with their own flavor of Ubuntu and KDE4 (https://en.wikipedia.org/wiki/LiMux) and more or less forced them to use this. They were using Kolab - https://en.wikipedia.org/wiki/Kolab and while I appreciate the effort if they really forced all users to use KDE Kontact with KDE4 I can understand that frustration was there. In my experience it's a UI nightmare and source of endless bugs. There is a difference between using out of personal interest or depending on it for work.

Their OpenOffice addons called WollMux was written in Java and at least judging from the screenshots is also an UI nightmare.

There was also criticism that the project was badly managed in parts and incompetence in the IT could have played a role.

These are all rumours, but it's believable.

Add to this that basically everyone else uses Outlook and MS Office and consider the difficulties when opening .docx stuff in LibreOffice and you can guess where the frustration might come from.

Another aspect is that Microsoft has quite a good story and technology with .NET and Active Directory / Group Policy and Powershell as well as .NET Integration to Office. Everything is accessible and .NET devs are plenty. Linux is more or less a wild garden of different solutions of different quality. This might contribute to the problems as more effort is needed to bring the software up to scratch. It's not something that is nice to hear but I can imagine that in the reality of public administration this stuff matters.

These might be reasons besides the political aspect of it. The polical stuff has some conspiracy touch to it and while I can image that a successful Linux toolkit for public administration that works well enough and can be deployed would easily kill Microsoft in that sector it's also likely that the opensource software is just lacking in some key aspects. Maybe it's a mixture of both.