Who is "we"? And what did they witness?
All we got right now is one side of the story.
It is indeed surprising such change wouldn't be immediately followed by a public announcement, but they've been founding and managing RubyGems for a very long time now, so it's not even clear to me how this can be a "takeover".
I'll happily join with my pitchfork if it turns out this is indeed a malevolent move, but until I've read their side of the story, I'd rather wait and see.
Edit: 35 minutes later, here we go: https://rubycentral.org/news/strengthening-the-stewardship-o...