I don't even think Linux is the definite answer. The majority of these critical apps are just full-screen UIs written in C, C++ or Java with minimal computing and networking, so they could just as easily run on Qubes or BSD without all the constant patching for dumb vulnerabilities that still persist even though Windows is 40 years old.
The problem is the middle management class at hospitals, governments, etc., only know how to use Word and maybe Excel, so they are comfortable with Microsoft, even though it's objectively the worst option if you aren't gaming. So then they make contracts with Microsoft and all the computers run Windows, so all the app developers have to write the apps for Windows.
The problem is the middle management class at hospitals, governments, etc., only know how to use Word and maybe Excel, so they are comfortable with Microsoft, even though it's objectively the worst option if you aren't gaming. So then they make contracts with Microsoft and all the computers run Windows, so all the app developers have to write the apps for Windows.