It kind of worked (I actually used it), but I don't think there was enough interest in it. Java is clearly dated on the JVM, but C# isn't that bad, and there is also F#. The CLR just doesn't need Scala as bad as the JVM did (and vice versa). There was never going to be a strong ecosystem there, even if there was a perfect version of scalac working.

You can easily erase to the CLR like you can on the JVM, the only issue is interop with .net APIs that use generics, of which this mostly means LINQ.