The language itself isn't 'more cool' or better, but the risk profile of adopting it has dropped dramatically. That makes it much more interesting.
My wife would leave me if she knew how much I love Kotlin, but I could never use it for work projects because we just could not justify expecting random inheriting developers to know Kotlin and accept its legitimacy. That constraint lifted in an instant. It's a political thing, but it really matters.
It is like hiring something who doesn't know the most used libraries in Android. And the risk is exactly the same. The language is not difficult to learn, not much more than a mid-complex library.
JetBrains was supporting kotlin for Android, the same people that build IntelliJ idea (the base of Android Studio). But who is supporting RxJava? Imagine that the react community wants to make a move that will harm Android devs, so they change all the Rx*, including RxJava.
Using kotlin wasn't a risk. Google said it will make it first class citizen, but do you really trust Google in the long term? They close products very quickly. I feel safer knowing that JetBrains is behind kotlin and not Google.
If I have an app with a codebase in a language that very few people know, that's a risk. What if my main developer leaves and I need to find someone else to continue working on the code base?
You can now bet that a lot of people will be picking up Kotlin as a result of the latest announcement.