Given the number of applications tied to running under a windows server, yes. Also, 80% of azure is running windows host environments... Many small-medium businesses are running a handful of windows servers, and most of them would prefer to simply install new applications on their already existing and under-loaded servers.
On the flip side, while I am more than happy to deploy new development projects to Linux hosts, and even in docker containers, I'm still stuck developing under windows, and having to run a VM to do most of my development isn't something I'm all that in favor of.
.Net developers mostly deploy to internal application servers.
That said, Azure is about the only cloud provider that really caters to .Net deployments, that is correct and probably accounts for a lot of it.
Me employer's next generation of applications is being deployed in Linux on Azure, because of their better support for our legacy applications (some will be around for quite a while)... which is part of why I said that "yes" running in windows is important.
If Node and Mongo didn't run in windows three years ago, we wouldn't be migrating to Linux today. I introduced Node in order to improve client-side web resources in a few web projects... once that was in place, it was a natural fit for one-off scripts (importers, timed tasks, etc). From there it became the API service for search (with mongodb behind IIS/ARR). Because of that, and the stability so far, it's our next generation platform. None of that would have happened without being able to run on windows.
On the flip side, while I am more than happy to deploy new development projects to Linux hosts, and even in docker containers, I'm still stuck developing under windows, and having to run a VM to do most of my development isn't something I'm all that in favor of.