> Why can’t the DoD say “ok we’re going with a different vendor”?

That's exactly what they're doing. It turns out the DoD is a really big bureaucracy and has process to make sure they thoroughly exclude a vendor and transitive dependencies on that same vendor.

They do, but this is not it. This is designating Anthropic as an adversary of the USA, and it is forbidding anyone who wants to sell to the DoD from using Anthropic products for anything. This is a massive attack on free speech, free enterprise, and the market.