I think rasmus's presentation explained pretty clearly why PHP won. Mod_php was a game changer and mod_perl failed by making the wrong choices. Overall, PHP was faster, easier, cutting edge and full of features without becoming too expensive to run, thats why web hosts supported it, not the other way around. What's not to love, honestly, even today.

https://www.youtube.com/watch?v=wCZ5TJCBWMg