React became popular, so companies adopted it because it was widely used and had a strong ecosystem. This led to more jobs requiring React. More developers learned React, which in turn led to more libraries, tutorials, and community contributions appearing. Increased resources and community support made it easier for new developers to start using React. Its popularity kept growing, which encouraged even more companies to adopt it.

The loop repeats.

Its popularity is self-reinforcing.

It’s also a major reason why React dominated the data that LLMs were trained on. You'll notice it's the default UI code when you prompt LLMs, unless you specify otherwise.

Personally, I prefer Svelte.