I don't mean to sound like a conspiracy theorist, and this is just based on my 33 years of observing the USG at work, so: maybe because Anthropic refused to cooperate with the USG and give them access to whatever it is that they (USG) wanted; or maybe because Anthropic was refusing to play ball in some other aspect and needed to be taught a lesson.

The dark parts of the USG act like a mafia. Don't let the "freedom, democracy, 'bill of rights'" etc. charade fool you.