|Keep It Simple, Stupid|
Okay, why do you think Ruby or Groovy made it?
Ruby made (in my opinion) for two reasons:
1) Design. a lot of people thought it had better design than Perl or Python (the other most popular languages at the time) actually most of those (a lot of) people I would say think it have a better design than any other language, it also wasn't haskell or Ocaml or lisp, meaning, it was not a new alien, it more or less came from the same paradigm as other popular language.
2) RoR.. Or in other words usefulness Ruby is useful, it have a popular framework that serve an important application dev area (dev development)
1) Usefulness . In this area Groovy hits it big, it leverage all of Java's heritage ++ Grails
2) Design. Again a lot of people agreed Groovy have a great design, at least compared to Java, also the design, was not an alien!
Might seem obvious! But Well, I believe making a language useful is a lot easier that claiming it have a better design compared to other languages. Better design, is very subjective! So the key part there was that a lot of people agreeed upon it and that it was not an alien!
I believe what we can really hope for is that Perl6 get the useful quality, few people would argue about this, and this could be also why its RoR or Grails (i.e. the killer app)that really drive those languages adoption (not undermining the none alien design)