The backers of Apache Groovy also tried the trick of sneaking in a new JVM language by offering tooling, testing, etc. But Groovy only had the dynamic language

The backers of Apache Groovy also tried the trick of sneaking in a new JVM language by offering tooling, testing, etc. But Groovy only had the dynamic language available, so there was nothing else there if people wanted to use it to build systems. They then opened up their AST via annotations to encourage people to build addons. Then after someone did build an addon (i.e. Groovy++) for static compilation, the Groovy backers built their own edition and bundled it in Groovy 2, thus killing all developer trust in the 3rd-party AST addon market. Unfortunately, the Groovy static compilation was built by only one developer and it still has QA issues. And it came too late -- many businesses still just host Groovy 1.x for legacy scripts. Kotlin, on the other hand, built the static compilation and Android targeting first, as the primary feature, and is offering the Repl and toplevel statements as extras. This is how languages are meant to work.