Me too [OP], as a M$H8r since in short trousers, finding that a platform that I like is implemented on a Windows stack challenges long-held prejudices, so, er, thanks?
More of a MS stack than a windows stack. If they are microservices and .net core, they are likely running Linux containers for hosting.
From my experience at a French company, Microsoft is very popular because they provide documentation and support in French.
That might have been the case in the past but nowadays every new server is Linux. MS still has a huge desktop and productivity footprint. Outlook/teams is the default. For my part, I have no choice but to log into my clusters from a Windows VM in some of kind of RDP.