It was succeeded by Angular (versions 2 and up), which is very popular for large complex apps at large companies. I think React, in the form of Next and other frameworks built around React, have finally caught up with the reason that made it so: more stuff "in the box", with decisions already made and already working.

If you have 200 Angular projects, there's a good chance developers can move between them without much difficulty. If you have 200 React projects, they might have 15 different combinations of selections for various accompanying libraries. This makes moving developers around harder (matters a lot in large organizations).

For example, nearly every Angular project uses Angular's CSS isolation mechanism plus Sass for complexities on other axes. Whereas there are various popular CSS solutions that divvy the React user community among them.

There are trade-offs, of course; Angular has so much in the box that so far nothing like Next (convention-based routing etc.) has sprung up around it. So I am quite bullish on React and Angular both - there will be lots of large important projects churning along with these in another decade, and beyond.

Also important to remember that these are just the two most popular; there are a couple of hundred other competing SPA frameworks that work very well for their intended use cases.