What makes Kotlin such a strong choice for many orgs today is its batteries-included multiplatform capability. We are able to write data models, validation logic, business logic, etc just once and compile to JVM, WASM, and native targets. For orgs with very large codebases and frontend applications (web + iOS + Android) this is an attractive capability because we can have a single codebase for a ton of core functionality, and have each frontend import a library which is native to its own platform.
Of course many technologies with this promise have come and gone over the years, but this is the first one with a strong backing that has allowed us to _natively_ interoperate with each target platform.
I believe these are all driving factors that have been pushing well known companies, that were previously Java shops, toward Kotlin. If you speak to a broad range of people in the industry you'll find many more orgs moving from Java to Kotlin than from Kotlin back to Java. We can simply get more work done with less code and ship to all our frontend platforms, and unless Java can do the same, I don't see the industry moving in that direction.