I think for a language to gain traction today in the mainstream, it needs to be backed by a large company. If the language is web technologies oriented, it's all the more likely. The reason is because lots of developers nowadays are working in web related stuff. And when it's backed by a big company like Google or Microsoft, kids will at least learn it to try and land a job at one of those companies. Also, these big companies will support many useful apis in that language which will attract mainstream developers as they can start building useful stuff quickly.

I wanted to learn a functional programming language and did a lot of research about which language to start with. Initially I looked at Haskell but ended up going with F# because the tooling was a lot better and the documentation from Microsoft was really good. Also, I read quite a few posts by those who worked fulltime, paid F# jobs. I loved the functional style. I think it's a shame that it's not mainstream. But then when I tried to do something non trivial, like network programming, I had to use OOP C# style types in F#. That was just fugly and made the paradigm look weak because OOP constructs could do it more easily than functional constructs.

Other than the elegance of the functional programming paradigm, it didn't seem to offer much in terms of jobs because I can't really see large numbers of people suddenly picking up functional programming (which isn't easy) and building massive applications specially with the whole cloud based SaaS stuff that's happening right now.