Google screwed Sun and had their opportunity to buy it.
The Java ecosystem has dozens of JVM implementations. None of them have ever had a problem with either Sun or Oracle.
Only Microsoft with their J++, and Google with their actions fragmenting the ecosystem for Java developers.
Microsoft learned their lesson and are now a OpenJDK contributor.
Time will come for Google as well.
Switching to Kotlin doesn't remove the dependency on the Java world, unless they plan to rewrite everything in Kotlin/Native.
There is some legal stuff going on as well: Java was being monetized by Oracle and Google needed a way out. This helps Kotlin a lot imho. When then free-Java case totally lost, Google allows all to move to Kotlin and IntelliJ has the code translator tool (and will prolly get bought by Google at some point).