In a free and uncorrupt country, you don't allow leaders to intervene in national security issues because they are embarrassed by a paper's coverage. Thus few people are directly saying that amazon should loose the bid because their CEO has a paper the president doesn't like.
More common and to be consistent with the notion of a corruption free democracy, the defense for this is the claim that, despite significant pressure, this surprising turn of events would have happened anyway. This is the story being promoted more but it does require a improbably interpretation of events that only supporters could really ever internalize. Especially since Trump's own secretary of defense flatly said the goal was to screw Amazon over the Post.