React also went through a lot of churn. (Still does.) There's no magic optimal duration for keeping API stability. Not in general and not for specific projects.
Ecosystems sometimes undergo a phase-shift. Sometimes they take a long time, based on the size. Python 3 was released in 2008, just a year before Angular 1. And the last Py2 release was in 2020, about 2-3 years before the last AngularJS version. (And of course there are many businesses running on py2 still. I know at least one.) These things take plenty of time.
Angular1 was pretty opinionated, willing to break with the tradition of just add one more jQuery plugin.
Miško was working at Google, he persuaded some people to take a look at the framework that he and Adam Abrons were tinkering with.
Angular 2 was announced in 2014 January. And then v1 still got years of support, even the component architecture was "backported" around 1.5 (in 2016?)
You can run old v1 code side-by-side in a v2+ app up until v17. (At least the v17 docs describe the process in full and later docs link to this page. https://v17.angular.io/guide/upgrade )
...
Google did a pretty good job IMHO. Google throws products under the bus, but not so much OSS projects. (Though the sate of AOSP comes to mind.)
I mean, I don't really like TypeScript, and I never have. It's ugly, boilerplatey, and inelegant. I am not a fan.
So... no.
But, again, some battles you have to accept you've lost. TS is everywhere and there's not much getting away from it.
It abandoned the Material Design web components project, which, I think, attracted some Polymer people.
Speaking of Polymer, it has evolved into Lit; but I understand there is no more support for that project from Google. Lit has joined the OpenJS foundation to stay afloat. The Googlers that used to work on Lit, and on Material Design web components have mostly left.
Also, remember the Workbox project? A simple setup for service workers? It's barely alive.