Earlier accessibility of a top Scheme implementation could have helped make it more popular earlier. Just like with Smalltalk and Common Lisp before which also got into trouble because of good implementations being out of reach of most people.
What about SCM, T, Larceny, Bigloo, Gambit, Chicken, Guile, and Racket? All were open source before Chez. T, in particular, while no longer active, was at the time a pioneer of fast and effective scheme compilation.
