It is truly mass hysteria, I would say that 95% of developers, project managers, and CTOs do not truly understand how these systems work under the hood, or at the very least are too scared and comfortable to try other systems. They just repeat the same things they hear and tell each other "react has a big ecosystem" "react is industry standard" "everyone uses react" "react was developed by facebook" "we will use react" "Developers only know react, how could we hire for a different framework?"
In my mind its clear that the alternatives are massively better. When i visit certain websites I often get a random tingle that it uses svelte because its way faster and has better loading and navigation than other sites and when i check the devtools I'm almost always correct.
I also get the same feeling sometimes when I hit a laggy slow webapp and I open the devtools and clearly see its a nextjs app.
A dev team could be trained on svelte or vue in literally 3 days, and so long as they actually understand how HTML, JS, and css work under the hood they would increase their speed massively. People just don't want to take the risk.