The reason is that LISP implementations that ran on "bog standard" hardware such as Motorola 68K, Intel 386 (and higher, but the 386 was released in 1985) and S

The reason is that LISP implementations that ran on "bog standard" hardware such as Motorola 68K, Intel 386 (and higher, but the 386 was released in 1985) and Sun's SPARC machines, could run reasonably well, while also being able to run compilers for other languages and a whole host of other apps. (Yes, there was a C compiler for the LISP machines from Symbolics.) So given the choice between "mainly LISP" and "LISP, C, Pascal, etc." from larger vendors that were virtually guaranteed to be around in 5 years, it was a rational choice to choose the bog-standard machines.