You are missing a massive part of the story. They are accusing the president of interfering in a public procurement process because of his personal dislike of Bezos/Amazon.
[1] https://aws.amazon.com/blogs/publicsector/jedi-why-we-will-c...
It seems that the massive part missed is that AWS claims Trump screwed with AWS.
Which may, legal or not, be a legitimate basis for complaint, but even if so it wouldn't mitigate the utterly indefensible and clearly corrupt (if true) conduct by the government Amazon describes after the selection criteria was set.
Contracting officials corruptly collaborating with Amazon to set the criteria doesn't excuse the DoD subsequently corruptly ignoring the selection criteria to hand the contract to Microsoft as political retribution based on the President’s animus toward Jeff Bezos.