The US may have gambled with the $2.5 billion dollar investment but it obviously paid off hugely and Moderna delivered essentially perfectly on their promises. I can understand why from their perspective they feel like they have already contributed quite a bit to ending the pandemic, at a very good price for the US taxpayer, and don't want to give away all their secrets.

I'm not defending the moral argument, but I think in terms of ROI you could only argue that Moderna got underpaid by the US government based on what they delivered.