The problem with that thesis is it has completely failed for Scheme (there are multiple Scheme implementations for the JVM, some are almost a decade old), and arguably for Common Lisp (ABCL came out at approximately the same time as Clojure, and although it's fairly popular as a Common Lisp implementation, it hasn't lead to major growth in adoption).
The reason I think the "it's Lisp but not really a Lisp" is a major factor is the example offered by newLISP. Its biggest thing seems to be "all this macro and lisp-2 and lexical scoping stuff is nonsense, this is not scheme or common lisp, this is a simple language," and despite this paradoxical assertion it has developed a somewhat large user community (a lot larger than Arc's, for example).
The JVM is much less of a factor than many people suggest. Another good example in support of this and the "concurrency" thesis is node.js - it's not the first JS web server (by far), and it's not the first NIO-based web server, but it does combine the two at the right time.
The reason I think the "it's Lisp but not really a Lisp" is a major factor is the example offered by newLISP. Its biggest thing seems to be "all this macro and lisp-2 and lexical scoping stuff is nonsense, this is not scheme or common lisp, this is a simple language," and despite this paradoxical assertion it has developed a somewhat large user community (a lot larger than Arc's, for example).
The JVM is much less of a factor than many people suggest. Another good example in support of this and the "concurrency" thesis is node.js - it's not the first JS web server (by far), and it's not the first NIO-based web server, but it does combine the two at the right time.