If those were the reasons for LISP's lack of popularity, then LISP would have been more popular than Python or PHP. What happened is that 1980s hardware was no

If those were the reasons for LISP's lack of popularity, then LISP would have been more popular than Python or PHP. What happened is that 1980s hardware was not ready for languages slower than C. C became the dominant language, and C-style syntax became the dominant syntax, with C++, Java and JavaScript following its lead. Eventually people adopted languages slower than C, but they didn't adopt paren-prefix notation.