Mind you, Kotlin/Native (which is what gets used when you're compiling for iOS) doesn't have access to the JVM.

However, the Kotlin community is fundamentally all about open source, whereas Apple & iOS Devs have an allergy to it. The quality and quantity is already miles above the vast majority of what's in the Swift ecosystem. https://klibs.io has all the native compatible libs. And if you're targeting a platform where the JVM is available then yeah, it's massive. Compose makes UI tolerable compared to JWT too. Even large projects like Spring are Kotlin first nowadays.

JetBrains has monetary interest in promoting Kotlin beyond Android, there’s zero incentive to promote Swift as the language outside of iOS and Mac. They don’t need to capture minds of devs for them to develop for Apple devices.