In the Netherlands, a lot of government systems aren't procured from the Microsofts of this world. There are a lot of middle men (consultancy agencies) involved that over the years have helped build a strong ecosystem with lots of expertise around Microsoft and related suppliers.
So indeed, it's not like you can just replace a software product (or service) by some EU or open alternative. And there are huge vested interests.
What makes you think they can't?
Microsoft's corporate edge isn't merely the product, it's also an army of sales, entrenched corporate markets/clients, lock-in, etc.
You could have a better version of their product and still get eaten alive.