I agree somewhat but there are other factors. You can't tell me that every web host worth their salt didn't (or doesn't) offer up a cgi-bin directory.
I would characterize it as this: PHP is a Perl-like language that is entirely web oriented.
Because Rasmus built PHP to make web sites it was oriented towards the web from day 1. Since it's similar to Perl (dynamic typing, just-in-time, etc) it's easy to learn and flexible.
However, unlike Perl there was no existing community with a non web focus. This made it very easy for the PHP community to rally around web projects and achieve all the things that made it good for the web and hence extremely adoptable.
I would characterize it as this: PHP is a Perl-like language that is entirely web oriented.
Because Rasmus built PHP to make web sites it was oriented towards the web from day 1. Since it's similar to Perl (dynamic typing, just-in-time, etc) it's easy to learn and flexible.
However, unlike Perl there was no existing community with a non web focus. This made it very easy for the PHP community to rally around web projects and achieve all the things that made it good for the web and hence extremely adoptable.