You're right, I just googled (actually Kagi'd) it and found:
With Google’s rollout of RCS as Android’s primary texting platform for Android Messages, many Android phones already come with Android Messages installed. A partnership between Google and Samsung allows RCS features to work seamlessly between the Samsung Messages and Android Messages apps, the default SMS apps on their devices. You can also go to the Google Play Store to download Messages yourself.
So that explains what happened, it still doesn't excuse forcing it, without permission or notice, on people who are using an open protocol