There is more to the AngularJS decline than simply something better coming along. The Angular team suffered from Fred Brook’s second system syndrome, as well as missing the need to design real backward compatibility into their system. The rise of react corresponds directly with the Angular team’s announcement that Angular 2 would not be backward compatible. 2014 was marked by a number of convulsions in the public release of the new system. I have to admit I was shocked at the low number of doc views for Angular 2+ docs shown in the keynote at ng-conf this year (AngularJS was still way more popular). I do find the lack of backward compatibility amusing as someone who worked on Windows at Microsoft for years. I can still run all my Turbo Pascal programs written 30 years ago in college in Windows 10!
All that said, I am very much liking Angular despite the team’s self inflicted wounds. The addition of typescript is great; and the tooling is a joy to develop in. I just wish the transition had been handled more gracefully.