This reminds me a lot of what happened (or didn't) to Tcl, although Lua has two major advantagen in LuaJIT and its "rocks" system, even though they probably could be exploited a bit more.

I think a general problem is the lack of a bigger standard library and access to libraries and APIs. Not needed as much if you use tcl/lua/scheme as an extension language, but pretty much essential for a stand-alone language. Note that even within the sector of new-fangled hyped languages (Rust, Go, Julia, Nim etc.), it might not be the one with the biggest library/package selection that wins -- or else we'd probably never stopped using Perl -- but it's pretty much required if you want to compete in the first place.