Java set out to solve two problems, one was portability of 'compiled' code, so OS/ISA independence, and the other was security issues. And Sun was actually in the process of flushing it down the toilet prior to the response it got in Darmdstadt and elsewhere. The big marketing push came when Sun saw it as a way to club Microsoft, that occurred only after people figured that 'life in the browser' didn't care what OS you ran on. And a lot of people wanted to get out from under Microsoft's thumb at the time.

"It seems that solving some problem might be optional, but commerical backing and long term support is essential."

It seems Forth might be a counter example here, what are your thoughts on its relative success?