Having worked for the French state and wrestled a few times with its IT services, I can tell you that the reason for choosing Microsoft isn't cost, or "efficiency".
It's that they only know Microsoft, they don't want to learn something else, and if there's a problem, it's Microsoft's fault, no theirs, so they don't have to deal with their own incompetence.
If you want an anecdote, we were working with SAS, a statistical software which required costly licences (more than a million € for a few dozens of workers). I suggested to switch to R or Python to the top director, who agreed.
First meeting with the service in charge, the chief opens with "ok, we are asked to change, but the goal here is to show that we tried, and found that it's not possible."
I resigned a few months after, as everything was in the same vein.
It's that they only know Microsoft, they don't want to learn something else, and if there's a problem, it's Microsoft's fault, no theirs, so they don't have to deal with their own incompetence.
If you want an anecdote, we were working with SAS, a statistical software which required costly licences (more than a million € for a few dozens of workers). I suggested to switch to R or Python to the top director, who agreed.
First meeting with the service in charge, the chief opens with "ok, we are asked to change, but the goal here is to show that we tried, and found that it's not possible."
I resigned a few months after, as everything was in the same vein.