Smalltalk predates pretty much all of "the toolchain", the first "real" version of Smalltalk is contemporary to UNIX Version 2. That's the one which added `echo`, and was installed on 10 machines. Smalltalk-72 predates both Emacs and VI ('76), "the toolchain" at the time was qed.
The early history of Smalltalk: http://gagne.homedns.org/~tgagne/contrib/EarlyHistoryST.html
I think Unix's success is much more about actual practical reasons that mere chance 'happening' to favour it.
Unix wasn't at all controlling and limiting in the way Smaltalk was. Unix provided complementary tools in an open environment. If you wanted to, you could write your own tools for Unix from the ground up starting from assembler even. The first thing people did on Unix was port over existing languages and tools such as Fortran from previous systems, and even to this day some of the base math libraries are implemented in Fortran. That sort of thing wasn't feasible with Smalltalk.
What I attribute more or less to "chance" (by which I basically just means the reasons are so multifarious that it's hard to say anything about them in general) is that Smalltalk didn't become more of a model for the desktop environments.
The big desktop environments are still mostly coded in C-like languages, although I guess it's changing slowly, especially with people becoming used to dynamic languages from web programming.
Of course, NeXTStep and OS X have a Smalltalk legacy, but they're not dynamic and interactive in the same way.
Another point is that since Smalltalk can be almost totally O/S independent, your images can run identically across platforms, including the entire development interface. And the development interface isn't separate from the "user" interface.
Regardless of Smalltalk's alleged death, the idea of having a system where you can interactively edit the source code of components is pretty radical, and will probably always be around. It's also kind of contrary to keeping source code proprietary, which might be an underrated reason for Smalltalk's unpopularity?
Sure it was.
The Genera Lisp Machines had compilers for C, Ada and Pascal available.
If one really wanted to have a Fortran compiler in a Smalltalk environment, s/he just needed to port it, just like Symbolics did for its Lisp Workstations.
Also Fortran and Prolog. Though added language were expensive. Usually it would also be useful to have a FPU option.
Thus a Lispm with Fortran would cost something like $100000 in the mid 80s. Which makes it possible to use Fortran, but not to an attractive price. ;-) 'Exotic systems' + software ported to exotic systems => expensive or not available. For decade the Symbolics approach was available and expensive, later it moved to 'mostly not available'...
Not true.
One effort I saw was a gigantic effort of using Smalltalk in a Very Large Insurance company. One of the tools they developed was one to read Cobol data divisions to get authoritative record formats for Smalltalk to use.
While revolutionizing the entire tool-chain at once is theoretically possible, it is also unlikely to succeed in practice. Successful tools and languages knew how to incrementally improve things within the current system. This may make some people angry, but that's how the world works (see the apocryphal but not entirely untrue story about the width of a horse and the size of the space shuttle). The reason is that decision makers need to reduce risks, and switching everything at once is risky and stupid. Perhaps that's a Nash equilibrium, but without something external to force a revolution, anyone fighting that equilibrium is likely to fail.