(a) In the heyday of DOS, people used all sorts of languages. Some of the first DOS programs I wrote were in Prolog.
(b) If the best hackers don't want to build stuff on your platform, you're in big trouble. Hard as it seems to imagine now, DOS was impressive in the mid 80s, and smart people wrote apps for it.
I don't think Google is deliberately courting mediocre hackers by using Java. It was probably just the expedient choice for some reason.