Just curious for those who have picked C# as their primary language your reasons?
My core reasons:
It was my first job out of college, it's what I'm most familiar with (as a startup person, moving fast is important)
Huge ecosystem of developers, add-ons, extensions, libraries, etc - many problems are "solved" by others, lots of help, forums, blog posts
Guided by MSFT. I like that the language is guided by a large company (as Rust, React are as well, Java to a lesser extent). It creates a forward momentum and lots of resources to making things better for users of the language
"Relatively" opinionated, you want to do rest API's, there's a clear pattern everyone uses, everyone has the same problems and similar needs - means the frameworks evolve in ways that make it easier for everyone. The new Throttle attribute's for API's a good example of something that lots of people need solutions for and there is now some out of the box support for it.
I started with BASIC on a C64, so Visual Basic was the natural progression when I moved to Windows development. When .NET was introduced, there was a lot of buzz around C# being a new language, and I decided, as a curiosity, to check it out. I was immediately hooked by its OOP-ness which was miles better than VB (though I understood VB.NET was functionally the same as C#) and I just stuck with it.
At this point, having used it for over twenty-some years, it's mostly inertia. I know they say to pick the best tool for the job, but in my career there's been little I haven't been able to do with it.