Installing any major work built in Perl back then was a nightmare of installing all the underlying dependency modules, often into the system directories. It didn't have a clean, standardized way to package up a script + dependencies easily, and dependency management was hellish, especially with many key modules needing platform-specific C compilation.
At that time commercial "shared" hosting was still common: many customers sharing one linux webhosting box and uploading scripts to via FTP, with no access to or control over the underlying system. If the webhost supported PHP, you could upload a php script and it Just Worked. Not so with Perl!
Perl was by far the superior language, but it just wasn't the superior experience for a beginning web developer who mostly just wanted to embed a tiny amount of CGI functionality in a static HTML page, and then upload and run it pretty much anywhere with no fuss.