ISTR a significant reason it died was the .Net platform's reified generics, which made making a language with generics and a type system more expressive than the underlying platform problematic, and especially made it difficult to have something that would be fully compatible with Scala-on-the-JVM.
That's not really true. Yes there are challenges with reified generics and yes Scala's generics don't fit. However you can work around it by doing the type erasure yourself. You can always consider a List[Int] to be a List[Any] and be done with it. And yes that's going to generate inefficient code, but ClojureCLR doesn't seem to mind.
No, the reason for why Scala.Net didn't happen is because nobody cared. To find proof of this, you only need to look at Clojure. Its .NET implementation is well maintained by David Miller, yet it's very unpopular. And the reason for why .NET developers don't care is because they don't have an open source culture. Or in other words, if it doesn't come from Microsoft, then it doesn't exist.
If you do erasure, then you can't also have the level of platform integration Scala has on the JVM: Scala on .NET either ends up as a different-but-similar language that isn't 100% compatible with Scala-on-JVM on a language level (as well the library differences), or its a second-class citizen that doesn't integrate well with the .NET platform, in which case, why have it?
So, in a sense, no on cared -- because neither of the available options was anything anyone wanted.
It died for technical reasons because .net supports reified generics, which made it pretty much unable to support Scala's type system.
People who keep saying that erased generics is a stupid idea have no idea what they're talking about.
scala-native is facing insurmountable difficulties, the kind that will certainly not be conquered by a single student who will stop working on it as soon as he graduates.