I'm being a bit provocative by highlighting corruption. It obviously has many factors:

* Training. During their studies, students, including those in IT, are inundated with Microsoft products.

* The ecosystem: training companies and service providers obviously support Microsoft products.

* In corporate IT services, choosing Microsoft as a standard solution is not a problem. It's not a problem if the project fails; it's the standard solution. However, making a different choice is a risk. Furthermore, on the IT staff side, having paid for Microsoft certification doesn't make them inclined to promote alternative solutions.

* And finally, the need expressed by users (fed Microsoft products, fueled by Microsoft marketing).

In short. But in a government service, things are a little different. Normally, the goal is budget efficiency and the effectiveness of public demand. Sovereignty can also be a goal.

In France, the army switched to Microsoft software. This was against the advice of a committee of experts who highlighted the risk of data leaks to a foreign power (not always friendly). French social security data is stored on Microsoft servers, against the advice of experts who highlighted the risk of data leaks (...) but this was agreed upon at the highest level. I can also mention the national education system, where the minister at the time reached an agreement introducing Microsoft into schools.

In short, Microsoft does a lot of lobbying at the highest level to promote its products. Sometimes it has gone further: I cited the admitted corruption of a Romanian minister by Microsoft.

And by the way, I remember reading (I can't find the sources) about the guy who organized the migration from Microsoft to Linux for the National Gendarmerie. He said that a condition for the project to succeed was that it not be known at the highest level. Otherwise Microsoft would have lobbied to discontinue it.