While I'm sure I'm also in a bubble, the numbers you present are far far off for instance Jetbrains' state of developer ecosystem reports. Where kotlin is roughly at 1/4th of javas usage, but for android quite high, and for backend up at 49 %

https://www.jetbrains.com/lp/devecosystem-2022/

Which matches what I've seen. Every single huge company or government function in Norway have the last years written most of the new code in their applications in kotlin. Basically all java conference talks I've seen has kotlin as the backdrop.

Kotlin's impact in preparing java devs for more functional code has been tremendous.