I don't think this is what happened. Anthropic could have absolutely complied with the government order, even in the most minimal fashion possible. Instead they chose to block everybody, and then give a link blaming the government.

I think it's most likely that they felt that this would drive wide antagonism towards the government which would help put them in a more favorable situation for future negotiations to establish a more 'commercially favorable regulation regime.' In other words, build me a moat, now! The government responded by super-screwing them, but is doing so in a way that can help keep the corporate class relatively content while this plays out.