Minestom is not based on Kotlin, im guessing they went with a kotlin template instead. Minestom is a server implementation that doesn't use any Mojang code and

Minestom is not based on Kotlin, im guessing they went with a kotlin template instead. Minestom is a server implementation that doesn't use any Mojang code and by default doesn't do much for you but provides the utilities to add the things yourself.