The value of hyperscalers' equity in Anthropic alone dwarfs their contracts with the government. Not to mention the revenue from hosting their models that helps justify the insane capex. Anthropic going to $0 would be a huge hair cut to all of their balance sheets.
They’ve only invested a couple of billions, like 20 or so split between them. Not really something that hurts them long or even medium term. Microsoft has multiple multi billion dollar government deals, I think Amazon is the only that doesn’t, Google also has a lot of government contracts, especially outside of cloud.