1. Some other AI company would cut a deal with the Pentagon. There's no world in which all the labs boycott the Pentagon. So who? Choosing Grok would be bad for the US, which is a bad outcome, but Amodei would have discounted that option, because he knows that despite their moral failures, the Pentagon is not stupid and Grok sucks.
That leaves Gemini or OpenAI, and I bet they predicted it would be OpenAI. Choosing OpenAI does not harm the republic - say what you will about Altman, ChatGPT is not toxic and it is capable - but it does have the potential to harm OpenAI, which is my second point:
2. OpenAI may benefit from this in the short term, and Anthropic may likewise be harmed in the short term, but what about the long game? Here, the strategic benefits to Anthropic in both distancing themselves from the Trump administration and letting OpenAI sully themselves with this association are readily apparent. This is true from a talent retention and attraction standpoint and especially true from a marketing standpoint. Claude has long had much less market share than ChatGPT. In that position, there are plenty of strategic reasons to take a moral/ethical stand like this.
What I did not expect, and I would guess Amodei did not either, is that Claude would now be #1 in the app store. The benefits from this stance look to be materializing much more quickly than anyone in favour of his courage might have hoped.