Scala had a decade head start. Many people at Google are aware of Scala, some being former LAMP students or staff. Google doesn't simply add a language to their small list of sanctioned toolchains.
Kotlin was specifically designed to win the politics argument, using technical merits: full interop, gradual adoption, low overhead, ability to target outdated Java bytecode efficiently (Kotlin used to inline lambdas for Java 6 bytecode for instance, while Scala boxed everything before invokedynamic). It doesn't matter whether one approach is objectively right or wrong, Kotlin fitted the bill and Scala did not. More importantly, Kotlin fitted the bill on Google's server side too!
Then of course JetBrains was tasked to replace the IDE with Android Studio, they could put dozens people backing Kotlin as a first-class Android language, until Google adopted it officially.
But even if Typesafe had somehow stumbled upon $100M in funding to do the same thing, it doesn't change the fact that Scala never had a chance.