You can run Scala on Android and it's been done but it never worked well nor was given priority. Which is understandable as the commercial entities behind Scala

You can run Scala on Android and it's been done but it never worked well nor was given priority. Which is understandable as the commercial entities behind Scala already struggle to build the ecosystem and tooling in spaces where the language shines. For instance the Android runtime has chronically lagged behind mainline JVM bytecode versions, iirc once Scala started to emit Java 8 bytecode, Android was stuck on Java 6. Kotlin had other obvious advantages on Android like its thin standard library or the inlining of higher-order functions.