Our nodeJS and angular deployments in Azure's managed app services are hosted in IIS.
If you are only counting the OS as an indication of .NET or no .NET, your numbers are severely inaccurate.
I could count on a single hand the amount of job postings for 'startup/startup-ish' companies that had a .net stack.
Edit: https://stackshare.io/application_and_data#! Somewhat anecdotal but still better than nothing..
Stack Overflow (and all the Stack Exchange sites) is in .NET
There are currently 200+ angel list jobs that require .NET
The stackshare link is not helpful because stackshare is something popular in the HN community. .NET is an incredibly popular framework outside of the SF/HN bubble. Startups around the globe and in middle America use .NET all the time.