That's a very good question! I think you have to look at each
language and see what the story is. I think most of the really big
ones involve some corporate backing at a certain point, or some kind
of 'lucky break'.
C was backed by Bell/AT&T, and was the language used to create Unix with.
Java had the full weight of Sun behind it, doing their best to get it
used by all kinds of other large corporations.
COBOL -
http://en.wikipedia.org/wiki/COBOL - looks like it had serious
backing from the US Government, as well as some pretty major
corporations.
Javascript had the 'lucky break' that it got included in browsers.
And so on.
--
David N. Welton
http://www.welton.it/davidw/
http://www.dedasys.com/