The Android APIs are all pretty much Java, so you need a JVM langauge to use them. The NDK requires a Java shim layer, and then you end up writing Java anyway to use most platform features.
Google obviously won't support competing first class toolkits on Android. You can already use most JVM languages on Android as is, especially since the switch to OpenJDK. Giving Kotlin first class support is just adding it to their own in house tools. You can already use Scala, for example, if you want.
Qt is a great example of how hard it is to bring a 3rd party language to Android. Qt app on Android cannot use native theme, cannot interact with most other apps, don't behave like other apps perfectly, and can be a mess to deploy because of how many Qt libraries you need to bundle in. Google doesn't actively stop you from shipping a Qt app on Android, but it took the Qt company a lot of work to get support where it is now, and its still far from seamless (if you want an example of a great Qt on Android app, try Subsurface Mobile that uses the Kirigami widget set).
Google obviously won't support competing first class toolkits on Android. You can already use most JVM languages on Android as is, especially since the switch to OpenJDK. Giving Kotlin first class support is just adding it to their own in house tools. You can already use Scala, for example, if you want.
Qt is a great example of how hard it is to bring a 3rd party language to Android. Qt app on Android cannot use native theme, cannot interact with most other apps, don't behave like other apps perfectly, and can be a mess to deploy because of how many Qt libraries you need to bundle in. Google doesn't actively stop you from shipping a Qt app on Android, but it took the Qt company a lot of work to get support where it is now, and its still far from seamless (if you want an example of a great Qt on Android app, try Subsurface Mobile that uses the Kirigami widget set).