> In November 2017 Munich city council decided to revert to Windows by 2020 with all systems being replaced by Windows 10 counterparts. Some of the reasons cited were adoption and users being unhappy with the lack of software available for Linux. A report commissioned by Munich and undertaken by Accenture, found the most important issues were organizational. > > In 2018, journalistic group Investigate Europe released a video documentary via German public television network ARD that claimed that the majority of city workers were satisfied with the operating system, with council members insinuating that the reversal was a personally motivated decision by lord mayor Dieter Reiter. Reiter denied that he had initiated the reversal in gratitude for Microsoft moving its German headquarters from Unterschleißheim back to Munich.

Basically corruption.

Source: https://en.wikipedia.org/wiki/LiMux

And for the documentary (watching it now, thank you!): https://archive.org/details/das-microsoft-dilemma

Two major reasons coinciding at the right time:

* They were alone. Munich is a big city ("biggest municipality in Germany" (there are bigger cities, but those are states as well)) but being an outlier complicated many things. For instance the software to order password from the federal printing agency was Windows only and required integration with hardware like fingerprint reader and stuff, being sole outlier makes this hard.

* Microsoft moved their German headquarters from a suburb to the city, thus pays local taxes.