> Why did the industry move on from PHP, and what was the problem with it?
Well, the problem is that PHP is a horrible language. Here is an article about it: https://eev.ee/blog/2012/04/09/php-a-fractal-of-bad-design/
I like how that article is not just a rant, but instead, it has a detailed list of some of the many issues that the language has.