Had these been picked for the IBM PC, it would have died and been replaced by some RISC.

Lisp machines only made any sense in that very brief window when DRAM was faster than the CPUs that used it. Partly because of process technology, partly because of lack of understanding of CPU design principles. With x86, you could choose to ignore the parts of the design that made it slow, and just build on the basics to bring the design forward. With a lisp machine, that would have never worked.

It wouldn't have been long until you would have been able to buy machines that would have been more than 10x faster on real workloads, and probably cheaper too.