I mean, in some ways JS truly is the new PHP. That is when you output some jsx template string, which conditionally has pseudo HTML elements (more components, but with HTML syntax) inside it, mixed with normal HTML tags, which in turn contain snippets of JS, which can have side effects ...

All of course preferred by the daily JS coder, instead of separating it out as one used to do with traditional template engines. PHP is the one that probably started this intermingling of everything, treating HTML as a mere string, instead of structured data, one of the biggest sins, leading to countless vulnerabilities over decades of web development. JS now carries on that torch of treating HTML wrong, only that the frameworks have apparently built in parsers or processing steps for their jsx, so that they find the web components and can separate them out from the surrounding HTML string, to evaluate them and output the HTML of those components into the surrounding HTML string.

JS also got the hallmarks of attracting a lot of beginners, just like PHP used to do, due to all the hype around JS frameworks. It is very tempting. You can quickly see the browser do something. With some backend language it will take much more, to see anything graphical. Seeing things move or change how something is displayed is a strong feedback and motivator for the beginner.