Modern languages and the JVM [duplicate]

Question

This question already has an answer here:

• What makes JVM so much versatile to support so many JVM languages? 5 answers

Many modern programming languages (Scala, Erlang, Clojure, etc.) are targeting the JVM. What are the main reasons behind that decision?

• JVM's maturity?
• Portability?
• Because JVM simply exists, and the language designers were not willing to write a new VM/interpreter?