I think it's too easy for them to give up or exit. Why don't they make another plan to continue Libra project? I am still sure that they can continue the project if they are serious to contribute to crypto world. Facebook is a big company and Zuckerberg must be aware of it!
Anyway, they look unprepared with USA regulation. It is a big mistake for sure, I don't believe they are not ready with that.
I think Zuckerberg has a backup plan and this announcement is just bluff! they know crypto world and Libra would continue to grow. I personally think this might attract even more attention to it.