BO's bid did not meet the basic requirements
They demanded to be paid in a way explicitly prohibited in the documents.
So NASA were contractually obliged to reject BO's bid anyway.
On top of that, the only thing they've actually got is an engine. It's a good engine, well designed and manufactured, supports multiple relights, throttles well and seems pretty reliable.
But an engine is not a rocket, as NASA well knows.
SpaceX were the only bidders who actually met the requirements.
Now, if Bezos was claiming the requirements were rigged, perhaps he'd have a case. But he's not.