[Mikera]

One of the reasons that Clojure has so many libraries is that most things didn't have to be implemented from scratch.

Building Clojure on the JVM was a genius move by Rich Hickey - it meant that an advanced runtime platform (the JVM) and a huge ready-to-use library ecosystem was already there from day 1.

Backwards compatibility with Common Lisp was never a goal. The JVM ecosystem is bigger by far (and IMHO more valuable as a target).